Test Description

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.

The numbers below refer to the step numbers on the diagnostic table.

2) - Listen for an audible click when the RAP#1 relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
3) - This step verifies that the Body Control Module (BCM) is providing ground to the RAP#1 relay.

Fig 1: DTC B1478 Diagnosis (Steps 1-5)

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC B1478 Diagnosis (Steps 6-9)

Courtesy of GENERAL MOTORS CORP.