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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 429 (Engine Controls Self-Diagnostics - 6.0L Bi-Fuel & CNG) >> Diagnostic Tests >> DTC P0300-P0308: Engine Misfire Detected >> Test Description

Test Description

WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 5

    This step determines if the engine is misfiring while operating on the gasoline fuel system.

  2. 7

    If the Misfire Current Counters are incrementing, but the engine is NOT misfiring, this indicates a mechanical condition. For example, an accessory drive belt could cause this condition.

  3. 8

    This step verifies that the Crankshaft Variation Learn Procedure is performed. A crankshaft variation that is not learned may cause the misfire counters to increment.

  4. 10

    The spark should be consistent when you test the spark at the spark plug wires. The presence of few sparks then nothing indicates no spark.

  5. 14

    A misfiring cylinder may cause more than one misfire counter to increment. Diagnose the fuel injector circuit of the cylinder that displays the highest level of misfire.

  6. 20

    This step verifies that the catalytic convertors are operating correctly.
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