Diagnostic Aids

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 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 in Lighting Systems.
Electromagnetic interference (EMI) on the vehicle speed sensor signal circuit may cause erratic cruise control operation.

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.