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Electronic Control System Gas Plus Engines – FAULT CODE 1649

Spark Voltage on Multiple Cylinders – Data Valid but Below Normal Operational Range

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Overview

CODE REASON EFFECT
Fault Code: 1649
PID: None
SPN: None
FMI: 1/17
LAMP: None
SRT: 

Spark Voltage on Multiple Cylinders – Data Valid but Below Normal Operational Range

None – information for misfire.

Ignition Timing Signal Circuit
SMALL | MEDIUM | LARGE

Circuit Description

The ICM is a distributorless ignition module that provides a signal to the coils and delivers high voltage to the spark plugs. The 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

This fault code is for information
only and does
not light a lamp when it becomes active. The fault is designed to inform the technician that a potential problem with the spark plugs, ignition coils, ignition harness, or ICM exists when the vehicle is in normal service or for misfire complaints. The most probable cause for this fault code to occur will be from an ignition coil or incorrectly gapped spark plug.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the status of engine misfire.  
  STEP 1A. Check for engine misfire. Engine misfiring?
STEP 2. Check the ignition coils.  
  STEP 2A. Inspect the ignition coils and connector pins. Dirty or damaged pins?
  STEP 2B. Check the spark plugs Visible damage or spark plug gap less than 0.30 mm [0.012 inch]?
STEP 3. Check the ICM, ignition coils and ignition harness.  
  STEP 3A. Inspect ICM 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 ignition coils. More than two coils not firing?
STEP 4. Clear the fault code.  
  STEP 4A. Disable the fault code. Fault Code 1649 inactive?
  STEP 4B. Clear the inactive fault codes. All fault codes cleared?

Guided Step 1 – Check status of engine misfire.

Guided Step 1A – Check for engine misfires.

Conditions

  • Turn keyswitch OFF.

Action

Check for engine misfire.

  • Interview the operator to see if there is any complaint of misfire.
  • Verify that the engine performs as the operator indicates with test drive or dynamometer test.

Engine misfiring?
YES NO
No Repair No Repair

Guided Step 2 – Check the ignition coils.

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

Conditions

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

Action

Inspect the ignition harness and ignition coil connector pins of the misfiring cylinders for the following:

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

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

Dirty or damaged pins?
YES NO

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

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 the spark plugs.

Conditions

  • Turn keyswitch OFF.

Action

Check for spark plugs with too small a spark gap.

  • Inspect the spark plugs for any damage
  • Use a feeler gauge to measure the spark plug gap.

Visible damage or spark plug gap less than 0.30 mm [0.012 inch]?
YES NO

Replace all damaged spark plugs. 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, ignition coils and ignition harness.

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

Conditions

  • Turn keyswitch OFF
  • Disconnect engine harness from the ICM connector C1.

Action

Inspect the ignition harness and ICM connector pins for the following:

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

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

Dirty or damaged pins?
YES NO

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

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

Conditions

  • Turn keyswitch OFF
  • Disconnect ignition harness connector C2 from the ICM.
  • Disconnect ignition harness from all coils.

Action

Check for an open circuit for each cylinder coil connector line.

  • Measure the resistance between the ignition harness ICM connector C2 coil SIGNAL pin and the ignition harness coil connector SIGNAL pin.
  • Measure the resistance between the ignition harness ICM connector C2 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 C2 from the ICM.
  • Disconnect ignition harness from all coils.

Action

Check for an open circuit.

  • Measure the resistance between the ignition harness ICM connector spark 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 C2. 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 C2 from the ICM
  • Disconnect the ignition harness from all coils.

Action

Check for a pin to ground short for each cylinder coil connector.

  • 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 C2 from the ICM.
  • Disconnect ignition harness from the ignition coils.

Action

Check for a pin to pin short.

  • Measure the resistance between the CD voltage pin in the ignition harness ICM connector C2 and all other pins in the ignition harness connector C2.
  • Measure the resistance between the spark RETURN SIGNAL pin in the ignition harness ICM connector C2 and all other pins in the ignition harness connector C2.
  • Measure the resistance between each coil SIGNAL pin in the ignition harness ICM connector C2 and all other pins in the ignition harness connector C2.

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 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.

Action

Check the ignition coils of all cylinders.

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

Note: Coil
must be tested in a vertical position or damage to the coil can result.

More than two coils
not firing?
YES NO
  • Replace the ICM. Refer to Procedure
    019-105.
  • 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 INSITE™ electronic service tool.

Action

Disable the fault code.

  • Start the engine and let it idle for 1 minute.
  • Use INSITE™ electronic service tool to verify that the fault code is inactive.

Fault Code 1649 inactive?
YES NO
No Repair No Repair

Guided Step 4B – Clear the inactive fault codes.

Conditions

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

Action

Clear the inactive fault codes.

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

All fault codes cleared?
YES NO
No Repair No Repair
Repair complete
Appropriate troubleshooting steps
Last Modified:  24-Jan-2007
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