Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Yukon, 2003 Chevrolet Tahoe, 2003 Chevrolet Suburban, and 2003 Chevrolet Avalanche. 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.
EMI on the vehicle speed sensor signal circuit may cause erratic cruise control operation.

For an intermittent condition, refer to TESTING WIRING SYSTEMS FOR INTERMITTENT & POOR CONNECTIONS in Wiring Systems.