Test Description

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.

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

4. Verifies that the body control module (BCM) is providing ground to the horn relay.

5. Tests for voltage at the battery positive voltage terminal of the horn relay coil.

7. Tests for voltage at the battery positive voltage terminal of the horn relay switch. The HORN fuse supplies power to the battery positive voltage terminal of the horn relay switch.

13. The horns need maximum current flow to operate properly. A high resistance (greater than 0.5 Ω) in the horn control circuit or the horn ground circuit could cause operating problems with the horns. Inspect the circuits for faults that would restrict current flow.

15. The horn relay control circuit includes the horn switch. The horn switch must be tested for a high resistance, an open or a short to voltage when testing the relay control circuit.

Fig 1: Horns Inoperative (Steps 1 - 10)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Horns Inoperative (Steps 11 - 21)

Courtesy of GENERAL MOTORS CORP.