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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 HHR 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Electronic Ignition (EI) System Diagnosis

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The ignition system uses individual ignition coil/module assemblies for each cylinder. The engine control module (ECM) controls the individual coils by transmitting timing pulses on the ignition control (IC) circuit of each ignition coil/module to enable a spark event. Each ignition coil/module has the following circuits:

    • Ignition 1 voltage
    • Ground
    • IC
    • Low reference

Diagnostic Aids
    • Depending on the location in the spliced ignition voltage circuit, a slight to moderate resistance can cause a misfire or a crank/no start concern.
    • Extended engine cranking time, will foul the spark plugs with excessive fuel and cause a crank/no start condition.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 26792 Spark Tester

Circuit/System Verification

Important: Verify that the engine is in good mechanical condition before continuing with this diagnostic.

    • Review the ignition system specifications and the spark plug inspection procedure to verify the following:
       - The ignition coil/modules are correctly connected
       - The proper firing order
       - The proper spark plug type
       - The proper spark plug gap and torque
       - Refer to Ignition System Specifications and Spark Plug Inspection.
    • If the engine will start, then observe the scan tool Misfire Current Cylinder parameters. This will indicate the affected ignition coil/modules.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the affected ignition coil/modules.
  2. Ignition OFF for 90 seconds, test for less than 5 ohms between the ground circuit terminal 1 and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 2 and ground.
    4. ⇒If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 4 and ground.
    5. ⇒If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance.
  5. Exchange the affected ignition coil/module with the ignition coil/module of a good cylinder.
  6. Start the engine, observe the scan tool Misfire Current Cylinder parameters.
    7. ⇒If the misfire transfers with the suspect ignition coil/module, replace it.
    ⇒If the misfire does not transfer with the suspect ignition coil/module, replace the spark plug.

Component Testing

Use the J 26792 to verify the output of each ignition coil/module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Ignition Coil Replacement
    •  Spark Plug Replacement