GM Service Manual Online
For 1990-2009 cars only

Checks

Action

Before Using This Section

Before using this section, you should have performed the On-Board Diagnostic System Check and determined that:

  1. The Control Module and the MIL (Malfunction Indicator Lamp) are operating correctly.
  2. There are no Diagnostic Trouble Codes (DTCs) stored, or a DTC exists but without an MIL.

Several of the following symptom procedures call for a careful visual and physical check. The visual and physical checks are very important. The checks can lead to correcting a problem without further checks which may save valuable time.

Visual and Physical Checks

    • Check the Control Module grounds for being clean, tight and in their proper location.
    • Check the vacuum hoses for splits, kinks and proper connections, as shown on the Vehicle Emission Control Information label.
    • Thoroughly check the mounting areas of the intake manifold sealing surfaces for any type of leak or restriction.
    • Check the wiring for the following items:
      • Proper connections
      • Pinches
      • Cuts
    • The following symptom tables contain groups of possible causes for each symptom and cover several engines. The following symptom tables cover several engines. The order of these procedures is not important. If the scan tool readings do not indicate the problems, then proceed in a logical order, easiest to check or most likely to cause first. In order to determine if a specific vehicle is using a particular system or component, refer to the Engine Schematic and Routing Diagrams for an application.

Symptom

Verify the customer complaint.

Locate the correct symptom table.

Check the items indicated under that symptom.