Electronic Control System Gas Plus Engines - Electronic Control System Gas Plus Engines - Troubleshooting and Repair Manual

Engine Performance Troubleshooting Tree

Symptoms

This troubleshooting procedure
must be followed for the following symptoms:

Engine Acceleration or Response Poor
Cranking Fuel Pressure is Low
Engine Operating Fuel Pressure is Low
Engine Decelerates Slowly
Engine Difficult to Start or Will Not Start (Exhaust Smoke)
Engine Difficult to Start or Will Not Start (No Exhaust Smoke)
Engine Power Output Low
Engine Runs Rough at Idle
Engine Runs Rough or Misfires
Engine Speed Surges at Low or High Idle
Engine Speed Surges Under Load or in Operating Range
Engine Shuts Off or Dies Unexpectedly or Dies During Deceleration
Engine Starts but Will Not Keep Running
Engine Will Not Reach Rated Speed (RPM)
Intake Manifold Pressure (Boost) is Below Normal

How To Use This Tree

This symptom tree can be used to troubleshoot all performance based symptoms listed above. Start by performing Step 1 troubleshooting. Step 2 will ask a series of questions and will provide a list of troubleshooting steps to perform depending on the symptom. Perform the list of troubleshooting in the sequence shown in the Specifications/Repair section of the tree.

Shop Talk

Driveability is a term that in general describes vehicle performance on the road. Driveability problems for an engine can be caused by several different factors. Some of the factors are engine-related and some are
not. Before troubleshooting it is important to determine the exact complaint and whether the engine has a real driveability problem or if it simply does
not meet driver expectations.

Low power is a term that is used in the field to describe many different performance problems. Low power is defined as the inability of the engine to produce the power necessary to move the vehicle at a speed that can be reasonably expected under the given conditions of load, grade, wind, and so on.

Poor acceleration or response is described as the inability of the vehicle to accelerate satisfactorily from a stop or from the bottom of a grade. It can also be the lag in acceleration during an attempt to pass or overtake another vehicle at conditions less than rated speed and load. Poor acceleration or response is difficult to troubleshoot since it can be caused by several factors.

Troubleshooting Steps

STEPS		SPECIFICATIONS
STEP 1.	Perform basic troubleshooting procedures.
	STEP 1A. Check for active fault codes or high counts of inactive fault codes.	Active fault codes or high counts of inactive fault codes?
	STEP 1B. Perform basic troubleshooting checks.	All steps have been verified to be correct?
STEP 2.	Determination of engine symptom.
	STEP 2A. Low power, poor acceleration, or poor response.	Is the engine symptom low power, poor acceleration, or poor response?
	STEP 2B. Engine misfire, engine speed surge, or engine speed unstable.	Is the engine symptom engine misfire, engine speed surge, or engine speed unstable?
	STEP 2C. Low intake manifold pressure.	Is the engine symptom Low Boost Pressure?
	STEP 2D. Engine will not start or difficult to start, engine shuts off unexpectedly.	Is the symptom Engine Will Not Start or Difficult to Start, Engine Shuts Off Unexpectedly?
STEP 3.	No-start troubleshooting procedures.
	STEP 3A. Check the engine speed during cranking.	Is the engine cranking speed greater than 150 rpm?
	STEP 3B. Check the ECM switched voltage at the ECM.	Is the switched voltage equal to the battery voltage?
	STEP 3B-1. Check the ECM key switch voltage at the 31 pin connector.
	STEP 3C. Check the ECM unswitched battery supply voltage.	Is the ECM battery SUPPLY voltage equal to the battery voltage?
	STEP 3C-1. Check the ECM unswitched voltage at the 23 pin connector.
	STEP 3D. Check for secondary fuel pressure while cranking the engine.	Is pressure correct for the platform?
	STEP 3D-1. Check primary fuel pressure while cranking the engine.
	STEP 3E. Check fuel control valve while cranking the engine.	Was the gas mass flow compensation measured by INSITE™ electronic service tool greater than plus or minus 90 percent?
	STEP 3F. Check the ECM for Sync Counts.	Are the sync counts greater than 7 and increasing?
	STEP 3G. Check the ignition coils.	Was a bad coil found on cylinders 3 and 4?
	STEP 3H. Check the spark plugs.	Were all spark plugs found to be failed?
	STEP 3I. Check for other fault codes that explain a no-start condition.	Do any fault codes that can cause a no-start condition come active during cranking?
STEP 4.	Fuel system troubleshooting procedures.
	STEP 4A. Check for secondary fuel pressure while cranking the engine.	Is pressure correct for the platform?
	STEP 4A-1. Check primary fuel pressure while cranking the engine.
	STEP 4B. Check fuel system for oil contamination.	Was the amount of oil greater than 28.3 grams [1 oz] or were there signs of oil contamination on the gas mass flow sensor?
	STEP 4C. Check fuel mixer for damage or debris.	Were cracks or debris found in the mixer sleeve?
	STEP 4D. Verify secondary fuel pressure sensor accuracy.	Is the Fuel Pressure-Secondary (INSITE™ electronic service tool) value within 14 kPa [2 psi]?
	STEP 4E. Verify primary fuel pressure sensor accuracy.	Is the Fuel Pressure-Primary (INSITE™ electronic service tool) value within 14 kPa [2 psi]?
	STEP 4F. Check the fuel control valve.	Did the fuel control valve compensation vary more than 3 percent.
	STEP 4G. Move on to the next system for low power, poor acceleration, or poor response.	Is the engine symptom low power, poor acceleration, or poor response?
	STEP 4G-1. Move on to the next system for engine misfire, engine speed surge, or engine speed unstable.
STEP 5.	Air handling troubleshooting procedures.
	STEP 5A. Inspect the turbocharger blades for damage.	Damage found on turbocharger blades?
	STEP 5B. Check the turbocharger axial and radial clearances.	Are the turbocharger axial and radial bearing clearances within specification?
	STEP 5C. Determination of turbocharger type.	Is the turbocharger a variable geometry turbocharger?
	STEP 5D. Check variable geometry actuator rod for correct travel.	Does the turbocharger actuator rod extend between 10.8 and 11.8 mm [0.42 and 0.46 in]?
	STEP 5D-1. Check for air leaks and inspect air lines.
	STEP 5D-2. Check for air pressure at the turbocharger control valve outlet.
	STEP 5D-3. Check for air pressure at turbocharger control valve outlet.
	STEP 5D-4. Check for vehicle air tank pressure at turbocharger control valve inlet.
	STEP 5D-5. Check for correct turbocharger actuator travel.
	STEP 5E. Check for broken shaft inside the turbocharger.	Does the sliding nozzle move correctly?
	STEP 5F. Inspect wastegate actuator hose or line.	Were holes or cracks found in the wastegate actuator hose?
	STEP 5G. Inspect wastegate control valve.	Does the air flow go into intake?
	STEP 5H. Inspect wastegate control valve vent to the atmosphere.	Does the air go to the atmosphere when +12 VDC is applied?
	STEP 5I. Inspect wastegate actuator rod for travel.	Does the wastegate actuator rod move? Note: All air handling Modes have been eliminated.
	STEP 5I-1. Inspect the wastegate actuator rod for travel.
	STEP 5J. Move on to the next system for low power, poor acceleration, or poor response.	Is the engine symptom low power, poor acceleration, or poor response?
	STEP 5J-1. Move on to the next system for engine misfire, engine speed surge, or engine speed unstable.
STEP 6.	Electronic feature troubleshooting procedures.
	STEP 6A. Verify accelerator pedal travel.	Does the accelerator position read 0 when the accelerator is released and 100 percent when the accelerator is depressed?
	STEP 6B. Verify electronic feature settings are correct.	Are the electronic features set correctly?
	STEP 6C. Check the sensor voltage supplies.	Is the supply voltage 4.0 to 5.0 VDC?
	STEP 6C-1. Check the ECM unswitched voltage at the 23 pin connector.
	STEP 6D. Check the ECM switched voltage at the ECM.	Is the switched voltage equal to the battery voltage?
	STEP 6D-1. Check the ECM key switch voltage at the 31 pin connector.
	STEP 6E. Check the mixer inlet pressure sensor accuracy.	Is the intake mixer inlet pressure reading barometric pressure?
	STEP 6F. Check manifold absolute pressure sensor accuracy.	Is the manifold absolute pressure reading barometric pressure?
	STEP 6G. Compare manifold absolute pressure sensor to mixer inlet pressure.	Are the two pressure readings within 7 kPa [1 psi]?
	STEP 6G-1. Compare manifold absolute pressure sensor to gauge pressure.
	STEP 6H. Check throttle actuator for proper operation.	Did the gas throttle control pass the test?
	STEP 6I. Determination of humidity sensor.	Does the engine have a humidity sensor?
	STEP 6I-1. Check humidity sensor accuracy.
	STEP 6J. Move on to the next system for low power, poor acceleration, or poor response.	Is the engine symptom low power, poor acceleration, or poor response?
STEP 7.	Base engine troubleshooting procedures.
	STEP 7A. Verify overhead adjustments are correct.	Are the overhead settings within the reset limits?
	STEP 7B. Inspect charge air cooler.	Is the charger air cooler free of cracks or damage?
	STEP 7C. Check air intake restriction.	Is air intake restriction greater than 635 mm H 2O [25 in H 2O]?
	STEP 7D. Check exhaust restriction.	Exhaust back pressure within 61 to 127 mm-Hg [2.4 to 5.0 in-Hg]?
	STEP 7E. Check engine cylinder leakage.	Are the engine differential pressure measurements greater than 60 percent?
	STEP 7F. Check engine blowby.	Are the engine blowby measurements within specification?
	STEP 7F-1. Verify turbocharger contribution to engine blowby.
	STEP 7G. Consult the next support level.	Have all steps been completed for the symptom?
STEP 8.	Ignition System troubleshooting procedures.
	STEP 8A. Inspect the spark plugs.	Were any spark plugs found to be failed?
	STEP 8B. Determination of coil type.	Are they coil on plug type?
	STEP 8B-1. Inspect the coil boots.
	STEP 8B-2. Inspect the plug wires.
	STEP 8C. Check the ignition control module (ICM) power supply.	Is the ICM power SUPPLY equal to the battery voltage?
	STEP 8D. Check ICM resistance.	Is the resistance check within specifications?
	STEP 8E. Check ignition coils.	Was a bad coil found?
	STEP 8F. Move on to the next system for low power, poor acceleration, or poor response.	Is the engine symptom low power, poor acceleration, or poor response?
STEP 9.	Open Loop troubleshooting procedures.
	STEP 9A. Operate the engine in Open Loop.	Did the vehicle performance change?
	STEP 9B. Check the sensor voltage supply 3.	Is the supply voltage +12.5 to 15.0 VDC?
	STEP 9B-1. Check the ECM unswitched voltage at the 23 pin connector.
	STEP 9C. Verify oxygen sensor operation.	Did the sensor pass the test?
	STEP 9D. Verify oil consumption rate.	Is the oil consumption high?
	STEP 9E. Verify overhead adjustments are correct.	Are the overhead settings within the reset limits?
	STEP 9F. Check the gas mass flow sensor compensation.	Is the gas mass flow compensation reading greater than ± 25 percent?

Guided Step 1 – Perform basic troubleshooting procedures.

Guided Step 1A – Check for active fault codes or high counts of inactive fault codes.
Conditions Turn keyswitch ON. Connect INSITE™ electronic service tool. Action Check for active fault codes. Use INSITE™ electronic service tool to read the fault codes.
Active fault codes or high counts of inactive fault codes?
YES	NO
Follow the electronic fault code trees for the appropriate troubleshooting procedures.	No Repair
Repair complete	Go to 1B

Guided Step 1B – Perform basic troubleshooting checks.
Conditions None. Action The following items must be checked or verified before continuing: Verify the fuel pressure in the tanks Verify the OEM fuel shut off valve is open. Verify there have not been any changes to CPL components on the engine. Verify the ECM calibration is correct for the engine. Verify fuel grade is correct for the application. Verify the engine is operating within the recommended altitude. Verify engine oil is at the correct level. Verify engine parasitic load has not changed. Verify engine duty cycle has not been changed. Verify battery voltage is above +12.5 VDC. Verify there are no fuel leaks.
All steps have been verified to be correct?
YES	NO
No Repair	Correct the failure and verify complaint is no longer present after repair.
Go to 2A	Repair complete

Guided Step 2 – Determination of engine symptoms.

Guided Step 2A – Low power, poor acceleration, or poor response.
Conditions None. Action Interview driver and verify the complaint. Interview the driver and verify the complaint.
Is the engine symptom low power, poor acceleration, or poor response?
YES	NO
Perform the troubleshooting steps in the recommended order listed below: Step 4 – Fuel system checks Step 9 – Open loop checks Step 8 – Ignition system checks. Step 5 – Air handling checks Step 6 – Electronics checks Step 7 – Base engine checks.	No Repair
Perform the troubleshooting steps suggested in the repair procedure	Go to 2B

Guided Step 2B – Engine misfire, engine speed surge, or engine speed unstable.
Conditions None. Action Interview driver and verify the complaint. Interview the driver and verify the complaints.
Is the engine symptom engine misfire, engine speed surge, or engine speed unstable?
YES	NO
Perform the troubleshooting steps in the recommended order listed below: Step 8 – Ignition system checks. Step 4 – Fuel system checks Step 9 – Open loop checks Step 6 – Electronics checks Step 5 – Air handling checks Step 7 – Base engine checks.	No Repair
Perform the troubleshooting steps suggested in the repair procedure.	Go to 2C

Guided Step 2C – Low intake manifold pressure.
Conditions None. Action Interview driver and verify the complaint. Interview the driver and verify the complaint.
Is the engine symptom Low Boost Pressure?
YES	NO
Perform the troubleshooting steps in the recommended order listed below: Step 5 – Air Handling Checks Step 4 – Fuel System Checks Step 7 – Base Engine Checks.	No Repair
Perform the troubleshooting steps suggested in the repair procedure	Go to 2D

Guided Step 2D – Engine will not start or difficult to start, engine shuts off unexpectedly.
Conditions None. Action Interview driver and verify the complaint. Interview the driver and verify the complaint.
Is the symptom Engine Will Not Start or Difficult to Start, Engine Shuts Off Unexpectedly?
YES	NO
Perform the troubleshooting steps in the recommended order listed below: Step 3 – No start checks Step 7- Base engine checks.	No Repair
Perform the troubleshooting steps suggested in the repair procedure	Return to correct symptom tree.

Guided Step 3 – No-start troubleshooting procedures.

Guided Step 3A – Check engine speed during cranking.
Conditions Turn keyswitch ON Connect INSITE™ electronic service tool. Action Crank the engine and monitor engine speed using electronic service tool. Use INSITE™ electronic service tool to monitor the engine speed during cranking.
Is the engine cranking speed greater than 150 rpm?
YES	NO
No Repair	Find and correct the cause of low cranking speed. Check the batteries, engine starting motor, and accessory loads. Consult the Engine Will Not Crank or Cranks Slowly troubleshooting tree.
Go to 3B	Repair complete

Guided Step 3B – Check the ECM switched voltage at the ECM.
Conditions Disconnect connector 2 from the ECM Turn the keyswitch ON. Action Measure the voltage on the switched input SIGNAL wires of the ECM connector 2 to the engine block ground. Note: Measure the key switch voltage with the key switch in the “ON” position and also with the key switch in the “Cranking” position. Refer to the wiring diagram for connector pin identification.
Is the switched voltage equal to the battery voltage?
YES	NO
No Repair	No Repair
Go to 3C	Go to 3B-1

Guided Step 3B-1 – Check the ECM key switch voltage at the 31 pin connector.
Conditions Disconnect the OEM harness from the 31 pin connector Turn the key switch ON. Action Measure the voltage on the switched input SIGNAL wires on the 31 pin connector to the engine block ground. Note: Measure the key switch voltage with the key switch in the “ON” position and also with the key switch in the “Cranking” position. Refer to the wiring diagram for connector pin identification.
Is the switched voltage equal to the battery voltage?
YES	NO
Repair or replace the harness between the 50 pin connector and 31 pin connector. Refer to Procedure 019-043.	Repair or replace the OEM power harness fuses, key switch, or check the battery connections.
Repair complete.	Repair complete.

Guided Step 3C – Check the ECM unswitched battery supply voltage.
Conditions Turn keyswitch OFF Disconnect connector 1 from the ECM. Action Measure the voltage from the ECM battery SUPPLY (-) negative to the ECM battery SUPPLY (+) positive pins of the 50 pin ECM connector 1. Note: Measure the ECM Voltage with the keyswitch in the “On” position and also with the keyswitch in the “Cranking”” position. Refer to the wiring diagram for connector pin identification.
Is the ECM battery SUPPLY voltage equal to the battery voltage?
YES	NO
No Repair	No Repair
Go to 3D	Go to 3C-1

Guided Step 3C-1 – Check the unswitched voltage at the 23 pin connector.
Conditions Disconnect the OEM harness from the 23 pin connector Turn keyswitch ON. Action Measure the voltage on the unswitched input SIGNAL wires of the 23 pin connector to the engine block ground. Note: Measure the ECM Voltage with the keyswitch in the “On” position and also with the keyswitch in the “Cranking”” position. Refer to the wiring diagram for connector pin identification.
Is the unswitched voltage equal to the battery voltage?
YES	NO
Repair or replace the harness between the 50 pin connector and the 23 pin connector. Refer to Procedure 019-043.	Repair or replace the OEM power harness, fuses, keyswitch, or check the battery connections.
Repair complete.	Repair complete

Guided Step 3D – Check for secondary fuel pressure while cranking the engine.
Conditions Turn keyswitch ON Connect a mechanical pressure gauge with a 0 to 689 kPa [0 to 100 psi] range. Action Measure the fuel pressure while cranking the engine. Remove the fuel pressure/temperature sensor and install a Compuchek® fitting and a mechanical pressure gauge. Refer to Procedure 019-153. Attempt to start the engine by engaging the engine starter for at least 30 continuous seconds. Note: All pressure sensors on the Gas Plus engines are absolute pressure sensors. The minimum values are: B Gas Plus – 414 kPa [60 psia] B LPG Plus – 276 kPa [40 psia] C Gas Plus – 517 kPa [75 psia] Note: Attempting to start the engine will assure the fuel shut off valve remains open.
Is pressure correct for the platform?
YES	NO
No Repair	No Repair
Go to 3E	Go to 3D-1

Guided Step 3D-1 – Check the primary fuel pressure while cranking the engine.
Conditions Turn the keyswitch ON Connect a mechanical pressure gauge with 0 to 1379 kPa [0 to 200 psi] range. Action Check the primary fuel pressure. Remove the fuel pressure sensor and install a Compuchek® fitting and a mechanical pressure gauge. Refer to Procedure 019-188. Attempt to start the engine by engaging the engine starter for at least 30 continuous seconds. Note: Attempting to start the engine will assure the fuel shut off valve remains open. Note: All pressure sensors on the Gas Plus engines are absolute pressure sensors. The minimum values are: B Gas Plus – 414 kPa [60 psia] B LPG Plus – 276 kPa [40 psia] C Gas Plus – 517 kPa [75 psia]
Is pressure correct for the platform?
YES	NO
Replace the low pressure regulator. Refer to Procedure 005-047 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206 and Procedure 005-047 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164.	Refer to the OEM troubleshooting of the high pressure regulator, shut off valve and restricted fuel lines.
Repair complete.	Repair complete.

Guided Step 3E – Check fuel control valve while cranking the engine.
Conditions Turn keyswitch ON. Connect INSITE™ electronic service tool. Action Crank the engine and use INSITE™ electronic service tool to monitor the gas mass flow compensation. Note: Attempting to start the engine will assure the fuel shut off valve remains open.
Was the gas mass flow compensation measured by INSITE™ electronic service tool greater than plus or minus 90 percent?
YES	NO
Replace the fuel control valve. Refer to Procedure 019-102.	No Repair
Repair complete	Go to 3F

Guided Step 3F – Check ECM for Sync Counts.
Conditions Turn keyswitch ON. Connect INSITE™ electronic service tool. Action Attempt to start the engine by engaging the engine starter for at least 30 continuous seconds. Connect INSITE™ electronic service tool. Monitor camshaft position sensor sync counts.
Are the sync counts greater than 7 and increasing?
YES	NO
Refer to Fault Code 753, Engine Position Sensor Synchronization Error.	No Repair
Repair complete.	Go to 3G

Guided Step 3G – Check Ignition Coils.
Conditions Refer to Procedure 013-012 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206 and in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164. Action Check ignition coils. Check for non-firing coils on cylinders 3 and 4. Note: A failure to the primary circuit on cylinders 3 or 4 will prevent all spark plugs from firing on engines with the three connector type ICM.
Was a bad coil found on cylinders 3 and 4?
YES	NO
Refer to Procedure 013-012 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206 and in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164.	No Repair
Repair complete.	Go to 3H

Guided Step 3H – Check Spark Plugs.
Conditions Refer to Procedure 013-016 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206 and in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164. Action Check the spark plugs. Check the spark plugs on all cylinders.
Were all spark plugs found to be failed?
YES	NO
Refer to Procedure 013-016 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206 and in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164.	No Repair
Repair complete	Go to 3I

Guided Step 3I – Check for other fault codes that explain a no-start condition.
Conditions Turn the keyswitch ON Connect INSITE™ electronic service tool. Action Use INSITE™ electronic service tool to check for fault codes that explain no-start condition. Use INSITE™ electronic service tool to read fault code information. Look for fault codes that come active during a failed start attempt that may be the cause for a “no start” condition.
Do any fault codes that can cause a no-start condition come active during cranking?
YES	NO
Follow the electronic fault code trees for the appropriate troubleshooting procedure.	No Repair
Repair complete.	Go to 7A

Guided Step 4 – Fuel system troubleshooting procedures.

Guided Step 4A – Check for secondary fuel pressure while cranking the engine.
Conditions Turn keyswitch ON Connect a mechanical pressure gauge with a 0 to 689 kPa [0 to 100 psi] range. Action Measure the fuel pressure while cranking the engine. Remove the fuel pressure/temperature sensor and install a Compuchek® fitting and a mechanical pressure gauge. Refer to Procedure 019-153. Attempt to start the engine by engaging the engine starter for at least 30 continuous seconds. Note: All pressure sensors on the Gas Plus engines are absolute pressure sensors. The minimum values are: B Gas Plus – 414 kPa [60 psia] B LPG Plus – 276 kPa [40 psia] C Gas Plus – 414 kPa [60 psia] L Gas Plus – 414 kPa [60 psia] Note: Attempting to start the engine will assure the fuel shut off valve remains open.
Is pressure correct for the platform?
YES	NO
No Repair	No Repair
Go to 4B	Go to 4A-1

Guided Step 4A-1 – Check the primary fuel pressure while cranking the engine.
Conditions Turn the keyswitch ON Connect a mechanical pressure gauge with 0 to 1379 kPa [0 to 200 psi] range. Action Check the primary fuel pressure. Remove the fuel pressure sensor and install a Compuchek® fitting and a mechanical pressure gauge. Refer to Procedure 019-188. Attempt to start the engine by engaging the engine starter for at least 30 continuous seconds. Note: Attempting to start the engine will assure the fuel shut off valve remains open. Note: All pressure sensors on the Gas Plus engines are absolute pressure sensors. The minimum values are: B Gas Plus – 414 kPa [60 psia] B LPG Plus – 276 kPa [40 psia] C Gas Plus – 414 kPa [60 psia] L Gas Plus – 414 kPa [60 psia]
Is pressure correct for the platform?
YES	NO
Replace the low pressure regulator. Refer to Procedure 005-047 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206 and Procedure 005-047 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164.	Refer to the OEM troubleshooting of the high pressure regulator, shut off valve and restricted fuel lines.
Repair complete.	Repair complete.

Guided Step 4B – Check fuel system for oil contamination.
Conditions Refer to Procedure 006-015 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206 and Procedure 006-015 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164. Refer to Procedure 019-101. Action Check for oil in the fuel filter. Drain the fuel filter. Measure the quantity of oil drained. Remove the gas mass flow sensor. Refer to Procedure 019-101. Inspect the gas mass flow sensor for oil contamination.
Was the amount of oil greater than 28.3 grams [1 oz] or were there signs of oil contamination on the gas mass flow sensor?
YES	NO
Clean the fuel system beginning at the low pressure regulator. Refer to Procedure 005-047 and 005-009 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164. Refer to Procedure 005-047 and 005-009 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.	No Repair
Repair complete	Go to 4C

Guided Step 4C – Check the fuel mixer for damage or debris.
Conditions Remove fuel mixer. Refer to Procedure 005-009 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 005-009 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206. Action Check fuel mixer for damage or debris. Remove fuel mixer. Refer to Procedure 005-009 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 005-009 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206. Inspect the mixer sleeve for debris and cracks.
Were cracks or debris found in the mixer sleeve?
YES	NO
Clean or replace the mixer sleeve. Refer to Procedure 005-009 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 005-009 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.	No Repair
Repair complete.	Go to 4D

Guided Step 4D – Verify secondary fuel pressure sensor accuracy.
Conditions Turn keyswitch ON. Connect INSITE™ electronic service tool. Install a pressure gauge at the elbow fitting on the fuel control housing. Refer to Procedure 005-047 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164. Refer to Procedure 005-047 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206. Action Check secondary fuel pressure sensor accuracy. Use INSITE™ electronic service tool to monitor Fuel Pressure – Secondary with the keyswitch ON and the engine not running. Remove the fuel pressure/temperature sensor and install a Compuchek® fitting and a mechanical pressure gauge. Refer to Procedure 019-153. Compare the two pressure readings.
Is the Fuel Pressure-Secondary (INSITE™ electronic service tool) value within 14 kPa [2 psi]?
YES	NO
No Repair	Replace the fuel pressure sensor. Refer to Procedure 019-153.
Go to 4E	Repair complete.

Guided Step 4E – Verify the primary fuel pressure sensor accuracy.
Conditions Turn keyswitch ON. Connect INSITE™ electronic service tool. Install a pressure gauge at the elbow fitting on the fuel control housing. Refer to Procedure 005-061 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164. Refer to Procedure 005-061 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206. Action Verify primary fuel pressure sensor accuracy. Use INSITE™ electronic service tool to monitor Fuel Pressure – Primary with the keyswitch ON and the engine not running. Remove the fuel pressure sensor and install a Compuchek® fitting and a mechanical pressure gauge. Refer to Procedure 019-188. Compare the two pressure readings.
Is the Fuel Pressure-Primary (INSITE™ electronic service tool) value within 14 kPa [2 psi]?
YES	NO
No Repair	Replace the fuel pressure sensor. Refer to Procedure 019-188 .
Go to 4F	Repair complete.

Guided Step 4F – Check Fuel Control Valve.
Conditions Refer to Procedure 019-102. Action Check the fuel control valve. Follow the initial steps in Procedure 019-102.
Did the fuel control valve compensation vary more than 3 percent?
YES	NO
Replace the fuel control valve. Refer to Procedure 019-102.	Note: All Fuel system Modes have been eliminated.
Repair complete.	Go to 4G

Guided Step 4G – Move on to the next system for low power, poor acceleration, or poor response.
Conditions All fuel system steps are complete. Action Move onto next system. Move onto the next system.
Is the engine symptom low power, poor acceleration, or poor response?
YES	NO
No Repair	No Repair
Go to 9A	Go to 4G-1

Guided Step 4G-1 – Move on to the next system for engine misfire, engine speed surge, or engine speed unstable.
Conditions All fuel system steps are complete. Action Move onto next system. Move onto the next system.
Is the engine symptom engine misfire, engine speed surge, or engine speed unstable?
YES	NO
No Repair	No Repair
Go to 6A	Go to 7A

Guided Step 5 – Air handling troubleshooting procedures.

Guided Step 5A – Inspect the turbocharger blades for damage.
Conditions Turn keyswitch OFF. Remove the intake and exhaust pipes from the turbocharger. Action Inspect the compressor and turbine blades for damage or wear. Refer to Procedure 010-033 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 010-033 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Damage found on turbocharger blades?
YES	NO
Replace the turbocharger assembly. Refer to Procedure 010-033 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 010-033 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.	No Repair
Repair complete	Go to 5B

Guided Step 5B – Check the turbocharger axial and radial clearances.
Conditions Turn keyswitch OFF. Action Check the turbocharger for correct axial and radial clearance. Refer to Procedure 010-038 and 010-039 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 010-033 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Are the turbocharger axial and radial bearing clearances within specification?
YES	NO
No Repair	Replace the turbocharger assembly. Refer to Procedure 010-033 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 010-033 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Go to 5C	Repair complete

Guided Step 5C – Determination of turbocharger type.
Conditions None Action Determine if the turbocharger is a wastegated or variable geometry turbocharger. Verify the type of turbocharger installed on the engine.
Is the turbocharger a variable geometry turbocharger?
YES	NO
No Repair	No Repair
Go to 5D	Go to 5F

Guided Step 5D – Check variable geometry actuator rod for correct travel.

Conditions

Turn keyswitch ON.
Connect INSITE™ electronic service tool.
Verify vehicle air tanks are fully charged (greater than 689 kPa [100 psi]).

Action

Use INSITE™ electronic service tool to start the Turbocharger Actuator Test

Adjust the delay timer in the Turbocharger Actuator Test so that the rod movement can be observed.
Select the Retract Actuator position with INSITE™ electronic service tool.
Mark or scribe the variable geometry actuator rod at the base of the actuator.
Select the Extend Actuator position with INSITE™ electronic service tool.
Measure the rod travel by measuring the distance from the base of the variable geometry actuator to the scribe mark.

Note: The variable geometry actuator
must move quickly and crisply. If the actuator rod movement is slow, there can be a problem with the air supply or mechanical problems with the variable geometry turbocharger assembly.

SMALL | MEDIUM | LARGE

Does the turbocharger actuator rod extend between 10.8 and 11.8 mm [0.42 and 0.46 in]?

YES

No Repair

Go to 5E

Go to 5D-1

Guided Step 5D-1 – Check for air leaks and inspect air lines.
Conditions Turn keyswitch ON. Connect INSITE™ electronic service tool. Verify vehicle air tanks are fully charged (greater than 689 kPa [100 psi]). Action Use INSITE™ electronic service tool to perform the Turbocharger Actuator Test. Select the Extended Actuator position and listen for air leaks in the following components: Turbocharger control valve Turbocharger control valve inlet connection Turbocharger control valve outlet connection Turbocharger actuator inlet connection Turbocharger actuator All air lines including OEM supply line to turbocharger control valve and between the turbocharger control valve and the variable geometry turbocharger. Note: A small amount of air will be heard escaping from the turbocharger control valve. This is a normal condition. Do not replace the turbocharger control valve for this condition.
Air leaks found in the system or damaged air lines?
YES	NO
Repair air leaks or replace damaged or broken air lines.	No Repair
Repair complete	Go to 5D-2

Guided Step 5D-2 – Check for air pressure at the turbocharger control valve outlet.
Conditions Turn keyswitch ON. Connect INSITE™ electronic service tool. Verify vehicle air tanks are fully charged (greater than 689 kPa [100 psi]). Action Remove the air line connection at the outlet of the turbocharger control valve. Install a Compuchek® fitting in the turbocharger control valve outlet. Install an air pressure gauge that is capable of reading at least 1034 kPa [150 psi]. Use INSITE™ electronic service tool to perform the Turbocharger Actuator Test. Select the Extend position.
Is vehicle tank air pressure present at the turbocharger control valve outlet?
YES	NO
No Repair	No Repair
Go to 5D-3	Go to 5D-5

Guided Step 5D-3 – Check for air pressure at turbocharger control valve outlet.
Conditions Turn keyswitch ON. Connect INSITE™ electronic service tool. Verify vehicle air tanks are fully charged (greater than 689 kPa [100 psi]). Action Remove the air line connection at the outlet of the turbocharger control valve. Install an air pressure gauge that is capable of reading at least 1034 kPa [150 psi]. Use INSITE™ electronic service tool to perform the Turbocharger Actuator Test. Select the Retract position.
Can air be heard escaping from the turbocharger control valve outlet?
YES	NO
The turbocharger control valve is stuck open. It must not be allowing air to escape when in the retract position. Replace the turbocharger control valve. Refer to Procedure 019-388.	No Repair
Repair complete	Go to 5D-4

Guided Step 5D-4 – Check for vehicle air tank pressure at turbocharger control valve inlet.
Conditions Turn keyswitch ON. Verify vehicle air tanks are fully charged (greater than 689 kPa [100 psi]). Action Disconnect the air inlet connection to the turbocharger control valve. Verify vehicle air tank pressure is available at the turbocharger control valve inlet.
Vehicle air tank pressure available at the turbocharger control valve inlet?
YES	NO
No Repair	No air pressure available at the turbocharger control valve inlet. Troubleshoot OEM air plumbing and determine why air pressure is not present.
Go to 5D-5	Repair complete

Guided Step 5D-5 – Check for correct turbocharger actuator travel.

Conditions

Remove the variable geometry actuator from the turbocharger assembly. Refer to Procedure
010-113 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Connect INSITE™ electronic service tool.

Action

Use INSITE™ electronic service tool to perform the Turbocharger Actuator Test.

Select the Extend Actuator position.

SMALL | MEDIUM | LARGE

Does the variable geometry actuator rod travel at least 12 mm [0.472 in]?

YES

The variable geometry actuator has correct air pressure and correct travel. The variable geometry mechanism in the turbocharger is seized.

Replace the turbocharger assembly. Refer to Procedure
010-033 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
010-033 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

The variable geometry actuator has correct air pressure but the variable geometry actuator rod is
not extending.

Replace the turbocharger actuator. Refer to Procedure
010-113 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

Repair complete

Guided Step 5E – Check for broken shaft inside the turbocharger.

Conditions

Turn keyswitch OFF.
Remove the variable geometry actuator from the turbocharger assembly. Refer to Procedure
010-113 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

Action

Check for a broken linkage inside the turbocharger by moving the variable geometry actuator on the turbocharger up and down.

The actuator lever
must move evenly and crisply as it is moved.

SMALL | MEDIUM | LARGE

Does the sliding nozzle move correctly?

YES

No Repair

The variable geometry has a mechanical failure inside the turbocharger. The actuator moves properly, but the linkage attaching the actuator to the nozzle is broken.

Go to 2A

Repair complete

Guided Step 5F – Inspect wastegate actuator hose/line.
Conditions Turn keyswitch OFF. Remove the wastegate actuator hose. Action Inspect the integral wastegate actuator hose for cracks or holes. Inspect the hose for damage.
Were holes or cracks found in the wastegate actuator hose?
YES	NO
Replace the wastegate actuator hose.	No Repair
Repair complete	Go to 5G

Guided Step 5G – Inspect wastegate control valve.
Conditions Turn keyswitch OFF. Remove the wastegate control hose/line. Action Apply a regulated air supply of 128 kPa [20 psi] to the wastegate control line connection. Apply a regulated air supply of 128 kPa [20 psi] to the wastegate control line connection on the wastegate control valve block.
Does the air flow go into intake?
YES	NO
No Repair	Replace the wastegate control valve. Refer to Procedure 019-103.
Go to 5H	Repair complete.

Guided Step 5H – Inspect wastegate control valve vent to atmosphere.
Conditions Turn keyswitch OFF Remove the wastegate control hose/line Remove the wastegate control valve electrical connector. Action Apply a regulated air supply of 128 kPa [20 psi] to the wastegate control line connection. Connect test leads to the pins on the wastegate control valve SUPPLY positive (+) to a +12 VDC supply positive (+) and the wastegate control valve SUPPLY negative (—) to a +12 VDC SUPPLY negative (—). Apply a regulated air SUPPLY of 128 kPa [20 psi] to the wastegate control line connection on the wastegate control valve block.
Does the air go to the atmosphere when +12 VDC is applied?
YES	NO
No Repair	Replace the wastegate control valve. Refer to Procedure 019-103.
Go to 5I	Repair complete.

Guided Step 5I – Inspect the wastegate actuator rod for travel.

Conditions

Turn the keyswitch OFF
Remove the integral boost line from the wastegate actuator.

Action

Apply a regulated air supply of 128 kPa [20 psi] to the wastegate actuator.

Apply a regulated air supply of 128 kPa [20 psi] to the wastegate actuator and check for actuator movement.

SMALL | MEDIUM | LARGE

Does the wastegate actuator rod move?

Note: All air handling Modes have been eliminated.

YES

No Repair

Go to 5J

Go to 5I-1

Guided Step 5I-1 – Inspect the wastegate actuator rod for travel.

Conditions

Turn the keyswitch OFF
Remove the integral boost line from the wastegate actuator.

Action

Apply a regulated air supply of 128 kPa [20 psi] to the wastegate actuator.

Apply a regulated air supply of 128 kPa [20 psi] to the wastegate actuator and check for actuator movement.

SMALL | MEDIUM | LARGE

Does the wastegate actuator rod move?

YES

Move the wastegate lever on the turbocharger back and forth and check for smooth operation.

Replace the turbocharger assembly if the wastegate is seized. Refer to Procedure
010-033 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
010-033 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

Replace the wastegate actuator. Refer to Procedure
010-050 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
010-050 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

Repair complete.

Guided Step 5J – Move on to the next system for low power, poor acceleration, or poor response.
Conditions All air handling steps are complete. Action Move on to next system. Move on to the next system.
Is the engine symptom low power, poor acceleration, or poor response?
YES	NO
No Repair	No Repair
Go to 6A	Go to 5J-1

Guided Step 5J-1 – Move on to the next system for engine misfire, engine speed surge, or engine speed unstable.
Conditions All air handling steps are complete. Action Move onto next system. Move on to the next system.
Is the engine symptom engine misfire, engine speed surge, or engine speed unstable?
YES	NO
No Repair	No Repair
Go to 7A	Go to 4A

Guided Step 6 – Electronic feature troubleshooting procedures.

Guided Step 6A – Verify accelerator pedal travel.
Conditions Turn keyswitch ON. Connect INSITE™ electronic service tool. Action Use INSITE™ electronic service tool to monitor Accelerator Position while fully depressing and releasing the accelerator pedal. Monitor Accelerator Position with INSITE™ electronic service tool while fully depressing and releasing the accelerator pedal.
Does the accelerator position read 0 when the accelerator is released and 100 percent when the accelerator is depressed?
YES	NO
No Repair	Determine and correct the cause of the accelerator pedal restriction.
Go to 6B	Repair complete

Guided Step 6B – Verify electronic feature settings are correct.
Conditions Turn keyswitch ON. Connect INSITE™ electronic service tool. Action With INSITE™ electronic service tool verify the following adjustable parameters are correctly set. Maximum vehicle speed Powertrain protection Rear axle ratio Tailshaft teeth Tire revolutions per mile Cruise control maximum vehicle speed.
Are the electronic features set correctly?
YES	NO
No Repair	Use INSITE™ electronic service tool to correct the programmable features.
Go to 6C	Repair Complete

Guided Step 6C – Check the sensor voltage supplies.
Conditions Turn keyswitch ON, engine running Connect INSITE™ electronic service tool. Action Use INSITE™ electronic service tool to monitor sensor supply voltage 1, 2 and 4. Use INSITE™ electronic service tool to monitor sensor supply voltage 1, 2 and 4.
Is the supply voltage 4.0 to 5.0 VDC?
YES	NO
No Repair	No Repair
Go to 6D	Go to 6C-1

Guided Step 6C-1 – Check the ECM unswitched voltage at the 23 pin connector.
Conditions Disconnect the OEM harness from the 23 pin connector Turn the keyswitch ON. Action Measure the voltage on the SIGNAL wires of the 23 pin connector to the engine block ground. Note: Measure the keyswitch voltage with the keyswitch in the “ON” position and also with the keyswitch in the “Cranking” position. Refer to the wiring diagram for connector pin identification.
Is the unswitched voltage equal to the battery voltage?
YES	NO
Repair or replace the harness between the 50 pin connector and the 23 pin connector. Refer to Procedure 019-043.	Repair or replace the OEM power harness, fuse, keyswitch, or check the battery connections.
Repair complete.	Repair complete.

Guided Step 6D – Check the ECM switched voltage at the ECM.
Conditions Disconnect connector 2 from the ECM Turn the keyswitch ON. Action Measure the voltage on the switched input SIGNAL wires of the ECM connector 2 to the engine block ground. Note: Measure the keyswitch voltage with the keyswitch in the “ON” position and also with the keyswitch in the “Cranking” position. Refer to the wiring diagram for connector pin identification.
Is the switched voltage equal to the battery voltage?
YES	NO
No Repair	No Repair
Go to 6E	Go to 6D-1

Guided Step 6D-1 – Check the ECM keyswitch voltage at the 31 pin connector.
Conditions Disconnect the OEM harness from the 31 pin connector. Turn the keyswitch ON. Action Measure the voltage on the switched input SIGNAL wires of the 31 pin connector to the engine block ground. Note: Measure the keyswitch voltage with the keyswitch in the “ON” position and also with the keyswitch in the “Cranking” position. Refer to the wiring diagram for connector pin identification.
Is the switched voltage equal to the battery voltage?
YES	NO
Repair or replace the harness between the 50 pin connector and the 23 pin connector. Refer to Procedure 019-043.	Repair or replace the OEM power harness, fuse, keyswitch, or check the battery connections.
Repair complete.	Repair complete.

Guided Step 6E – Check mixer inlet pressure sensor accuracy.
Conditions Turn keyswitch ON, no engine speed Connect INSITE™ electronic service tool. Action Use INSITE™ electronic service tool to monitor the value of the mixer inlet pressure without the engine running. Note: The present barometric pressure in psi is determined by multiplying the local weather station barometric pressure in inches of mercury by 0.4911.
Is the intake mixer inlet pressure reading barometric pressure?
YES	NO
No Repair	Replace the mixer inlet pressure sensor. Refer to Procedure 019-098.
Go to 6F	Repair complete.

Guided Step 6F – Check manifold absolute pressure sensor accuracy.
Conditions Turn keyswitch ON, no engine speed Connect INSITE™ electronic service tool. Action Use INSITE™ electronic service tool to monitor the value of the manifold absolute pressure without the engine running. Note: The present barometric pressure in psi is determined by multiplying the local weather station barometric pressure in inches of mercury by 0.4911.
Is the manifold absolute pressure reading barometric pressure?
YES	NO
No Repair	Replace the manifold absolute pressure sensor. Refer to Procedure 019-099.
Go to 6G	Repair complete.

Guided Step 6G – Compare manifold absolute pressure sensor to mixer inlet pressure.
Conditions Turn keyswitch ON, engine at stall condition Connect INSITE™ electronic service tool. Action Use INSITE™ electronic service tool to monitor the values for the manifold absolute pressure and mixer inlet pressure. Use INSITE™ electronic service tool to monitor the value of manifold absolute pressure with the engine running under stall conditions.
Are the two pressure readings within 7 kPa [1 psi]?
YES	NO
No Repair	No Repair
Go to 6H	Go to 6G-1

Guided Step 6G-1 – Compare manifold absolute pressure sensor to gauge pressure.
Conditions Turn keyswitch ON, engine at stall condition. Connect INSITE™ electronic service tool. Remove the mixer inlet sensor and install a mechanical gauge. Action Use INSITE™ electronic service tool to monitor the values for the manifold absolute pressure. Use INSITE™ electronic service tool to monitor the value of manifold absolute pressure with the engine running under stall conditions. Monitor the reading of the mechanical gauge and compare it to the reading in INSITE™ electronic service tool.
Are the two pressure readings within 7 kPa [1 psi]?
YES	NO
Replace the mixer inlet pressure sensor. Refer to Procedure 019-098.	Replace the manifold absolute pressure sensor. Refer to Procedure 019-099.
Repair complete.	Repair complete.

Guided Step 6H – Check throttle actuator for proper operation.
Conditions Turn keyswitch ON Connect INSITE™ electronic service tool. Action Verify proper throttle operation. Use INSITE™ electronic service tool to activate the gas throttle control test.
Did the gas throttle control pass the test?
YES	NO
No Repair	Repair or replace the throttle actuator. Refer to Procedure 005-052 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 005-052 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Go to 6I	Repair complete.

Guided Step 6I – Determination of humidity sensor.
Conditions None Action Verify the engine is equipped with a humidty sensor. Determine if the engine is equipped with a humidity sensor.
Does the engine have a humidity sensor?
YES	NO
No Repair	No Repair
Go to 6I-1	Go to 6J

Guided Step 6I-1 – Check humidity sensor accuracy.

Conditions

Turn keyswitch ON, no engine speed
Humidity sensor removed from intake plumbing
Connect INSITE™ electronic service tool.

Action

Use INSITE™ electronic service tool to monitor the value of the humidity sensor.

Use the psychrometric chart to determine the current grains/lb of humidity.

Use current temperature and relative humidity.
Find where temperature (vertical lines) and relative humidity (curved lines) intersect on the plot and read absolute humidity (horizontal lines).

The default value of the humidity sensor is 75 grains/lb.

SMALL | MEDIUM | LARGE

Is the humidity sensor reading current absolute humidity within ±10 grains?

YES

No Repair

Replace the humidity sensor. Refer to Procedure
019-356

Go to 6J

Repair complete.

Guided Step 6J – Move on to the next system for low power, poor acceleration, or poor response.
Conditions All electronic features steps are complete. Action Move on to next system. Move on to the next system.
Is the engine symptom low power, poor acceleration, or poor response?
YES	NO
No Repair	No Repair
Go to 7A	Go to 5A

Guided Step 7 – Base engine troubleshooting procedures.

Guided Step 7A – Verify overhead adjustments are correct.
Conditions Turn keyswitch OFF. Remove the rocker lever cover. Refer to Procedure 003-011 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 003-011 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206. Action Measure the overhead setting. Refer to Procedure 003-004 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 003-004 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Are the overhead settings within the reset limits?
YES	NO
No Repair	Adjust the overhead settings. Refer to Procedure 003-004 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 003-004 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Go to 7B	Repair complete

Guided Step 7B – Inspect the charge air cooler.

Conditions

Refer to Procedure
010-027 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
010-027 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

Action

Inspect the charge air cooler.

Inspect the charge air cooler for cracks, holes, or damage. Refer to Procedure
010-027 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
010-027 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

SMALL | MEDIUM | LARGE

Is the charger air cooler free of cracks or damage?

YES

No Repair

Repair or replace the charge air cooler. Refer to Procedure
010-027 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
010-027 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

Go to 7C

Repair complete

Guided Step 7C – Check air intake restriction.

Conditions

Refer to Procedure
010-031 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
010-031 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

Action

Check the intake system restriction.

Check the intake system restriction by installing a vacuum gauge into the air intake system. Refer to Procedure
010-031 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
010-031 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

SMALL | MEDIUM | LARGE

Is air intake restriction greater than 635 mm H
₂O [25 in H
₂O]?

YES

Correct the cause of high intake air restriction. Check for plugged air filter or restricted air intake piping.

Refer to Procedure
010-031 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
010-031 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

No Repair

Repair complete

Go to 7D

Guided Step 7D – Check exhaust restriction.

Conditions

Refer to Procedure
011-009 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
011-009 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

Action

Check the exhaust system back pressure.

Check the exhaust system back pressure by installing a pressure gauge into the exhaust system just past the turbocharger outlet. Refer to Procedure
011-009 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
011-009 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

SMALL | MEDIUM | LARGE

Exhaust back pressure within 61 to 127 mm-Hg [2.4 to 5.0in-Hg]?

YES

No Repair

Inspect exhaust system for source of high restriction. Refer to Procedure
011-009 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure
011-009 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.

Go to 7F

Repair complete

Guided Step 7E – Check engine cylinder leakage.
Conditions Refer to Procedure 014-012. Action Meassure engine cylinder differential pressure. Measure the engine cylinder differential pressure as outlined in Procedure 014-012. Determine percent differential pressure by dividing gauge two value with gauge one value then multiply by 100.
Are the engine differential pressure measurements greater than 60 percent?
YES	NO
No Repair	Remove the cylinder head and inspect valves, valve seats, piston rings, and cylinder condition for source of cylinder leakage. Refer to Procedures 002-004 and 001-043 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedures 002-004 and 001-043 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Go to 7F	Repair complete.

Guided Step 7F – Check engine blowby.
Conditions Refer to Procedures 014-005 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164 and 014-005 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206. Action Measure the engine blowby. Measure the engine blowby as outlined in Procedure 014-005 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164 and 014-005 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Are the engine blowby measurements within specification?
YES	NO
No Repair	No Repair
Go to 7G	Go to 7F-1

Guided Step 7F-1 – Verify turbocharger contribution to engine blowby.
Conditions Turn keyswitch OFF. Connect the appropriate orifice to the end of the blowby draft tube. Remove the turbocharger oil drain line from the block and drain into a bucket. Start the engine. Action Load engine to rated rpm on a chassis dynamometer. Measure the engine blowby as outlined in Procedure 014-005 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164 and 014-005 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Has the total engine blowby dropped more than 30 percent of the total?
YES	NO
Replace the turbocharger assembly. Refer to Procedure 010-033 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 010-033 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.	Repair or replace the air compressor assembly. Refer to Procedure 012-014 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 012-014 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Repair complete	Repair complete

Guided Step 7G – Move to the next support level.
Conditions None Action Review all data collected to this point. Have all data collected available.
Have all steps been completed for the symptom?
YES	NO
Move to the next level of support.	Return to the steps not completed for the symptom.
Repair complete.	Repair complete.

Guided Step 8 – Ignition System troubleshooting procedures.

Guided Step 8A – Inspect the spark plugs.
Conditions Refer to Procedure 013-016 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206. Action Inspect the spark plugs. Inspect the spark plugs on all cylinders.
Were any spark plugs found to be failed?
YES	NO
Replace the spark plugs. Refer to Procedure 013-016in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.	No Repair
Repair complete.	Go to 8B

Guided Step 8B – Determination of coil type.
Conditions None Action Determine which type of coils are installed. Determine if the coils are coil packs or coil on plugs.
Are they coil on plug type?
YES	NO
No Repair	No Repair
Go to 8B-1	Go to 8B-2

Guided Step 8B-1 – Inspect the coil boots.
Conditions Engine off. Action Inspect coil on plug boots. Inspect the coil on plug boots for damage.
Was damage found on the coil boot?
YES	NO
Replace boots. Refer to Procedure 013-012 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.	No Repair
Repair complete.	Go to 8C

Guided Step 8B-2 – Inspect spark plug wires.
Conditions Refer to Procedure 013-014 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164. Action Inspect spark plug wires. Inspect all the spark plug wires for wear, damage and resistance.
Was damage found on any spark plug wires?
YES	NO
Replace the damaged spark plug wire(s). Refer to Procedure 013-014 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus.	No Repair
Repair complete.	Go to 8C

Guided Step 8C – Check the ICM power supply.
Conditions Refer to procedure 019-105. Action Measure the switched battery voltage to the ICM. Measure the voltage on the switched battery SUPPLY positive (+) pin to the battery RETURN negative (-) pin to the ICM. Note: Measure the voltage with the keyswitch in the “ON” position and also with the keyswitch in the “Cranking” position. Refer to the wiring diagram for connector pin identification.
Is the ICM power SUPPLY equal to the battery voltage?
YES	NO
No Repair	No Repair
Go to 8D	Go to 6D-1

Guided Step 8D – Check the ICM resistance.
Conditions Refer to Procedure 019-105. Disconnect the ICM connectors. Action Measure the ICM resistance. Follow the resistance check found in the initial check in Procedure 019-105.
Is the resistance check within specifications?
YES	NO
No Repair	Replace the ICM. Refer to Procedure 019-105.
Go to 8E	Repair complete.

Guided Step 8E – Check the ignition coils.
Conditions Refer to Procedure 013-012 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206. Action Inspect the ignition coils. Follow initial check procedure. Follow resistance check procedure. Note: A failure to the primary circuit on cylinders 3 or 4 will prevent all the plugs from firing.
Was a bad coil found?
YES	NO
Replace the bad coil(s). Refer to Procedure 013-012 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.	No Repair
Repair complete.	Go to 8F

Guided Step 8F – Move on to the next system for low power, poor acceleration, or poor response.
Conditions All ignition system steps are complete. Action Move onto next system. Move onto the next system.
Is the engine symptom low power, poor acceleration, or poor response?
YES	NO
No Repair	No Repair
Go to 5A	Go to 4A

Guided Step 9 – Open Loop troubleshooting procedure.

Guided Step 9A – Operate the engine in Open Loop.
Conditions Connect INSITE™ electronic service tool. Test drive the vehicle. Action Lock the engine in Open Loop. Use INSITE™ electronic service tool to lock the engine in the Open Loop and drive the vehicle.
Did the vehicle performance change?
YES	NO
No Repair	No Repair
Go to 9B	Go to 9F

Guided Step 9B – Check sensor voltage supply 3.
Conditions Turn the keyswitch ON, engine running Connect INSITE™ electronic service tool. Action Monitor sensor voltage supply 3. Use INSITE™ electronic service tool to monitor sensor voltage supply 3.
Is the supply voltage +12.5 to 15.0 VDC?
YES	NO
No Repair	No Repair
Go to 9C	Go to 9B-1

Guided Step 9B-1 – Check the ECM unswitched voltage at the 23 pin connector.
Conditions Disconnect the OEM harness from the 23 pin connector. Turn the keyswitch ON. Action Check the ECM unswitched voltage. Measure the voltage on the unswitched input SIGNAL wires of the 23 pin connector to the engine block ground. Note: Measure the keyswitch voltage with the keyswitch on the “ON” position and also with the keyswitch in the “Cranking” position. Refer to the wiring diagram for connector pin identification.
Is the unswitched voltage equal to the battery voltage?
YES	NO
Repair or replace the harness between the 50 pin connector and 23 pin connector. Refer to Procedure 019-043.	Repair or replace the OEM power harness, fuses, keyswitch, or check the battery connections.
Repair complete.	Repair complete.

Guided Step 9C – Verify oxygen sensor operation.
Conditions Connect all components. Start and idle engine for 3 minutes. Stop engine. Turn keyswitch ON. Connect INSITE™ electronic service tool. Action Perform the Heated Oxygen Sensor test using the INSITE™ Electronic Service Tool. Use INSITE™ electronic service tool to activate the Heated Oxygen Sensor test. Follow the directions given by the INSITE™ electronic service tool.
Did the sensor pass the test?
YES	NO
No Repair	Replace the heated oxygen sensor. Refer to Procedure 019-100. Use INSITE™ electronic service tool to reset the fuel tables.
Go to 9D	Repair complete

Guided Step 9D – Verify oil consumption rate.
Conditions Interview driver. Action Check oil consumption against mileage. Check the amount of oil consumption against the mileage.
Is the oil consumption high?
YES	NO
Follow the Lubricating Oil Consumption Excessive troubleshooting tree.	No Repair
Repair complete.	Go to 9E

Guided Step 9E – Verify overhead adjustments are correct.
Conditions Turn keyswitch OFF. Remove the rocker lever cover. Refer to Procedure 003-011 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 003-011 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206. Action Measure the overhead setting. Refer to Procedure 003-004 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 003-004 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Are the overhead settings within the reset limits?
YES	NO
No Repair	Adjust the overhead settings. Refer to Procedure 003-004 in the Troubleshooting and Repair Manual B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666164, and Procedure 003-004 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus and L Gas Plus Engines, Bulletin 3666206.
Go to 9F	Repair complete

Guided Step 9F – Check the gas mass flow sensor compensation.
Conditions Turn keyswitch ON, engine running Connect INSITE™ electronic service tool. Action Use INSITE™ Electronic Service Tool to monitor the value of gas mass flow sensor compensation. Use INSITE™ electronic service tool to monitor the value of gas mass flow compensation with the engine running at a stall condition.
Is the gas mass flow compensation reading greater than ± 25 percent?
YES	NO
Replace the gas mass flow sensor. Refer to Procedure 019-101.	Engine has an ignition related engine misfire. Follow steps in Step 8.
Repair complete.	Go to 8A

Last Modified: 04-Dec-2009

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