GM Service Manual Online
For 1990-2009 cars only

Before Using This Section

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

  1. The control module and the malfunction indicator lamp (MIL) are operating correctly.
  2. There are no diagnostic trouble codes (DTCs) stored, or a DTC exists but without a 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 following items:

    • The control module grounds for being clean, tight and in their proper location.
    • The vacuum hoses for splits, kinks, and proper connections, as shown on the Vehicle Emission Control Information label.
    • The wiring for the following items:
       - Proper connections
       - Pinches
       - Cuts
    • The following symptom tables contain groups of possible causes for each symptom. 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 Emission Hose Routing Diagram or Engine Controls Schematics for an application.

Verify Customer's Concern

Locate the correct symptom table. Check the items indicated under that symptom from the following symptom tables:

    •  Intermittent Conditions
    •  Hard Start
    •  Surges/Chuggles
    •  Lack of Power, Sluggishness, or Sponginess
    •  Fuel Knock/Combustion Noise
    •  Hesitation, Sag, Stumble
    •  Cuts Out, Misses
    •  Poor Fuel Economy
    •  Excessive Smoke