GM Service Manual Online
For 1990-2009 cars only

Checks

Action

Before Using this Section

    • Perform the Alternative Fuels (AF) Powertrain On-Board Diagnostic (OBD) System Check before using this section.
    • Determine if the following conditions are present:
       - The control module and the Malfunction Indicator Lamp (MIL) are operating properly.
       - There are no Diagnostic Trouble Codes (DTCs) stored or a DTC exists but without an MIL.
    • Several of the following symptom procedures require a careful visual and physical check .
    • The visual and physical checks are very important.
    • These checks can lead to correcting a problem without further checks, which may save valuable time.

Visual and Physical Checks

    • Verify that the control module grounds are clean, tight and in their proper location.
    • Inspect the vacuum hoses for leaks, splits, kinks and proper connections. This information is shown on the Vehicle Emission Control Information Label.
    • Inspect thoroughly for any type of fuel leak or fuel line restriction.
    • Check for air leaks at all the mounting areas of the intake manifold sealing surfaces.
    • Verify proper installation of the Gas Distribution Adapter (GDA).
    • Check for air leaks at the GDA.
    • Inspect the ignition wires for the following conditions:
       - Cracking
       - Hardness
       - Proper routing
       - Carbon tracking
    • Inspect the wiring for the following conditions:
       - Proper connections
       - Pinches
       - Cuts
    • The following symptom tables contain groups of possible causes for each symptom. The order of these procedures is not important. Proceed in a logical order if the scan tool readings do not indicate the problems. Start with the easiest to check or most likely to cause first.

Symptoms

  1. Verify the customer concern.
  2. Locate the correct symptom table.
  3. Inspect the items indicated under that symptom.