Diagnostic Aids

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Important:

Remove any debris from the TAC module connector surfaces before servicing the TAC module. Inspect the TAC module connector gaskets when diagnosing/replacing the module. Ensure that the gaskets are installed correctly.
For any test that requires probing the PCM or a component harness connector, use a connector test adapter. Using a connector test adapter prevents damage to the harness/component terminals. Refer to USING CONNECTOR TEST ADAPTERS .
Inspect for a set/coast switch stuck in the engaged position or the signal circuit is shorted to voltage.
For an intermittent refer to TESTING FOR INTERMITTENT & POOR CONNECTIONS .