Diagnostic Aids

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Perform the following in order to avoid a misdiagnosis:

Inspect for proper operation of the brake lamps. Refer to EXTERIOR LIGHTING SYSTEMS DESCRIPTION AND OPERATION .
EMI on the vehicle speed sensor signal circuit may cause erratic cruise control operation.

For an intermittent condition, refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS .