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Electronic Control System Gas Plus Engines – FAULT CODE 1271

Engine Misfire for Multiple Cylinders – Data Valid but Below Normal Operational Level – Most Severe Level

Overview

CODE REASON EFFECT
Fault Code: 1271
PID: None
SPN: 1322
FMI: 1
LAMP: Red
SRT: 

Engine Misfire for Multiple Cylinders – Data Valid but Below Normal Operational Level – Most Severe Level

Progressive power derate increasing in severity from time of alert.

Ignition Timing Signal Circuit
SMALL | MEDIUM | LARGE

Circuit Description

The ignition control module (ICM) is a distributorless ignition module that provides a signal to the coils and delivers high voltage to the spark plugs. The electronic control module (ECM) controls the ICM by providing ignition timing information. The ICM is capable of misfire and spark voltage detection.

Component Location

The ICM is located next to the ECM on the side of the engine.

Shop Talk

For the ICM to operate correctly, all components must be clean and tight. Fault Codes 1482 will always be active if this fault is active.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the status of misfire.  
  STEP 1A. Check for an inactive fault code. Fault Codes 1271 inactive?
  STEP 1B. Check for spark plug voltage fault codes. Fault Codes 613, 1649, 1651, or 1652 active?
  STEP 1B-1. Check for multiple fuel system fault codes.
  STEP 1C. Check the life of spark plug. Spark plugs life is between 50 and 1400 hours?
STEP 2. Check the ignition coils and spark plugs.  
  STEP 2A. Inspect the ignition coils and connector pins. Dirty or damaged pins?
  STEP 2B. Check for voltage at the coils. Steady spark observed?
  STEP 2C. Check the spark plugs Spark plug damaged or wear?
STEP 3. Check the ICM and ignition harness.  
  STEP 3A. Inspect ICM, ignition coils and ignition harness connector pins. Dirty or damaged pins?
  STEP 3B. Check for an open circuit in the ignition harness. Less than 10 ohms?
  STEP 3B-1. Check for an open circuit in the ignition harness.
  STEP 3C. Check for a pin short circuit to ground. Greater than 100k ohms?
  STEP 3D. Check for a pin to pin short circuit in the ignition harness. Greater than 100k ohms?
  STEP 3E. Check the ICM. ICM to specification?
  STEP 3F. Verify that ignition coils and ignition circuit are good. Steady spark observed?
STEP 4. Clear the fault code.  
  STEP 4A. Disable the fault code. Fault Code 1271 inactive?
  STEP 4B. Clear the inactive fault codes. All fault codes cleared?

Guided Step 1 – Check status of misfire.

Guided Step 1A – Check for an inactive fault code.

Conditions

  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

  • Run the vehicle in the condition in which the misfire occurred.
  • Use INSITE™ electronic service tool to read the fault codes.

Fault Code 1271 inactive?
YES NO
No Repair No Repair

Guided Step 1B – Check for spark plug voltage fault codes.

Conditions

  • Turn keyswitch OFF
  • Connect INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to read the fault codes.

Fault Codes 613, 1649, 1651, or 1652 active?
YES NO
No Repair No Repair
Fault Codes 613, 1649, 1651, or 1652 before proceeding

Guided Step 1B-1 – Check for multiple fuel system fault codes.

Conditions

  • Turn keyswitch OFF
  • Connect INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to read the fault codes.

Fault Codes 2184, 2219, 751, or 752 active?
YES NO

Troubleshoot any remaining fault codes before proceeding.

Note: If any of these fault coders are present, then the misfire can be due to a system error. Such as, engine running lean or gas mass flow sensor or heated oxygen sensor can not compensate correctly.

 No Repair
Fault Codes 2184, 2219, 751, or 752 before proceeding

Guided Step 1C – Check the life of spark plugs.

Conditions

  • Refer to the Maintenance Schedule, in Procedure 102-002 of the C8.3G, C Gas Plus, and L Gas Plus Owners Manual, Bulletin 4021387.

Action

  • Refer to the Maintenance Schedule, in Procedure 102-002 of the C8.3G, C Gas Plus, and L Gas Plus Owners Manual, Bulletin 4021387 for the last time the spark plugs where changed.

Spark plugs life is between 50 and 1400 hours?
YES NO
No Repair No Repair

Guided Step 2 – Check the ignition coils and spark plugs.

Guided Step 2A – Inspect ignition coil and connector pins.

Conditions

  • Turn keyswitch OFF
  • Disconnect ignition harness from the ignition coil.

Action

  • Corroded pins
  • Bent or broken pins
  • Pushed back or expanded pins
  • Wire insulation damage
  • Moisture in or on the connector
  • Missing or damaged connector seals
  • Connector shell broken
  • Dirt or debris in or on the connector pins.

For general inspection techniques, refer to Component Connector and Pin Inspection, Procedure 019-361.

Dirty or damaged pins?
YES NO

A defective connection has been detected in the ignition coil or ignition harness connectors.

Repair the damaged pins. Repair or replace the harness, whichever has the damaged pins.

  • Repair the harness. Refer to Procedure 019-202.
  • Replace the ICM. Refer to Procedure 019-105.
 No Repair

Guided Step 2B – Check for voltage at the coils.

Conditions

  • Turn keyswitch ON
  • Refer to Procedure 013-012 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206.

Action

  • Test each coil one at a time to determine if the coils are receiving voltage.
  • Using the Ignition Coil Test Kit, Part Number 4918343, observe the spark in the observation window.

Steady spark observed?
YES NO
No Repair No Repair

Guided Step 2C – Check the spark plugs.

Conditions

  • Turn keyswitch OFF
  • Remove the spark plug from the misfiring cylinders.

Action

  • Insulation flashover
  • Electrode deposits or fouling
  • Worn or missing electrode
  • Cracked insulator
  • Electrode misalignment
  • Gap between 0.30 to 0.38 mm [0.012 to 0.015 inch].

Spark plug damage or wear?
YES NO

Replace each damaged spark plug. Refer to Procedure 013-016 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206.

 No Repair

Guided Step 3 – Check the ICM and ignition harness.

Guided Step 3A – Inspect the ICM and ignition harness connector pins.

Conditions

  • Turn keyswitch OFF
  • Disconnect engine harness from the ECM.

Action

  • Corroded pins
  • Bent or broken pins
  • Pushed back or expanded pins
  • Wire insulation damage
  • Moisture in or on the connector
  • Missing or damaged connector seals
  • Connector shell broken
  • Dirt or debris in or on the connector pins.

For general inspection techniques, refer to Component Connector and Pin Inspection, Procedure 019-361.

Dirty or damaged pins?
YES NO

A defective connection has been detected in the ICM, ignition coils or ignition harness connector.

Repair the damaged pins. Repair the harness, whichever has the damaged pins.

  • Repair the harness. Refer to Procedure 019-202.
  • Replace the ICM. Refer to Procedure 019-105.
 No Repair

Guided Step 3B – Check for an open circuit in the ignition harness.

Conditions

  • Turn keyswitch OFF
  • Disconnect ignition harness connector 2 from the ICM.
  • Disconnect ignition harness from all coils.

Action

  • Measure the resistance between the ignition harness ICM connector 2 coil SIGNAL pin and the ignition harness coil connector SIGNAL pin.
  • Measure the resistance between the ignition harness ICM connector 2 CD voltage pin and the ignition harness coil connector CD voltage pin.

Refer to the circuit diagram or wiring diagram for connector pin identification.

For general resistance measurement techniques, refer to Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360

Less than 10 ohms?
YES NO
No Repair

An open signal circuit has been detected in the ignition harness.

Repair or replace the ignition harness.

  • Replace the ignition harness. Refer to Procedure 013-037 in the Troubleshooting and Repair Manual C Gas, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206.

Guided Step 3B-1 – Check for an open circuit in the ignition harness.

Conditions

  • Turn keyswitch OFF
  • Disconnect ignition harness connector 2 from the ICM.
  • Disconnect ignition harness from all coils.

Action

  • Measure the resistance between the ignition harness ICM connector 2 coil RETURN SIGNAL pin and the ignition harness coil connector RETURN SIGNAL pins.

Note: All spark return signal wires in the ignition harness are tied together. This way there will be continuity through each spark signal pin of each coil to the main spark return signal wire at the ignition harness connector 2. If one of the spark signal circuits is found to be open, then the ICM will think that the engine is misfiring when it is not.

Refer to the circuit diagram or wiring diagram for connector pin identification.

For general resistance measurement techniques, refer to Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360

Less than 10 ohms?
YES NO
No Repair

A open signal circuit has been detected in the ignition harness.

Repair or replace the ignition harness.

  • Replace the ignition harness. Refer to Procedure 013-037 in the Troubleshooting and Repair Manual C Gas, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206.

Guided Step 3C – Check for a pin short to ground.

Conditions

  • Turn keyswitch OFF
  • Disconnect the ignition harness connector 2 from the ICM
  • Disconnect the ignition harness from all coils.

Action

  • Measure the resistance between the CD voltage pin at the coil connector and engine block ground.
  • Measure the resistance between the coil SIGNAL pin at the coil connector and engine block ground.
  • Measure the resistance between the spark SIGNAL pin at the coil connector and engine block ground.

Refer to the circuit diagram or wiring diagram for connector pin identification.

For general resistance measurement techniques, refer to Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360

Greater than 100k ohms?
YES NO
No Repair

A pin to ground short circuit has been detected in the ignition harness.

Repair or replace the ignition harness.

  • Replace the ignition harness. Refer to Procedure 013-037 in the Troubleshooting and Repair Manual C Gas, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206.

Guided Step 3D – Check for a pin to pin short circuit in the ignition harness.

Conditions

  • Turn keyswitch OFF
  • Disconnect ignition harness connector 2 from the ICM.
  • Disconnect ignition harness from the ignition coils.

Action

  • Measure the resistance between the CD voltage pin in the ignition harness ICM connector 2 and all other pins in the ignition harness connector 2.
  • Measure the resistance between the spark RETURN SIGNAL pin in the ignition harness ICM connector 2 and all other pins in the ignition harness connector 2.
  • Measure the resistance between each coil SIGNAL pin in the ignition harness ICM connector 2 and all other pins in the ignition harness connector 2.

Refer to the circuit diagram or wiring diagram for connector pin identification.

For general resistance measurement techniques, refer to Resistance Measurements Using a Multimeter and Wiring Diagram, Procedure 019-360

Greater than 100k ohms?
YES NO
No Repair

A pin to pin short circuit has been detected in the ignition harness.

Repair or replace the ignition harness.

  • Replace the ignition harness. Refer to Procedure 013-037 in the Troubleshooting and Repair Manual C Gas, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206.

Guided Step 3E – Check the ICM.

Conditions

  • Refer to Procedure 019-105 to test the ICM.

Action

  • Refer to Procedure 019-105 to test the ICM.

ICM to specification?
YES NO
No Repair
  • Replace the ICM. Refer to Procedure 019-105.

Guided Step 3F – Verify that ignition coils and ignition circuit are good.

Conditions

  • Refer to Procedure 013-012 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206.

Action

  • Using the Ignition Coil Test Kit, Part Number 4918343, observe the spark in the observation window.

Steady spark observed?
YES NO
No Repair

Replace the ignition coil. Refer to Procedure 013-012 in the Troubleshooting and Repair Manual C8.3G, C Gas Plus, and L Gas Plus Engines, Bulletin 3666206.

Guided Step 4 – Clear the fault codes.

Guided Step 4A – Disable the fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect the INSITE™ electronic service tool.

Action

  • Start the engine and let it idle for one minute.
  • Use INSITE™ electronic service tool to verify that the fault code is inactive.

Fault Code 1271 inactive?
YES NO
No Repair No Repair

Guided Step 4B – Clear the inactive fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect the INSITE™ electronic service tool.

Action

  • Use INSITE™ electronic service tool to erase the inactive fault codes.

All fault codes cleared?
YES NO
No Repair No Repair
Repair complete
Appropriate troubleshooting steps
Last Modified:  30-Sep-2004
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