Diagnostic Procedure
- Turn ignition on, engine off. Using scan tool, command horn relay ON and OFF. If relay follows scan tool command, problem is intermittent. If relay does not follow scan tool command, go to next step.
- Check HORN fuse (10-amp). If fuse is blown, repair as necessary. If fuse is okay, remove horn relay. Connect a test light between horn relay connector terminals No. 28 and 1540. See Fig 1
. Using scan tool, command horn relay ON and OFF. If test light follows scan tool command, check horn relay connector. If connector is okay, replace horn relay. If test light is always on, repair short to ground in Black wire between horn relay and BCM. See WIRING DIAGRAMS
. If test light is always off, go to next step.
- Connect test light between horn relay connector terminal No. 1540 and ground. See Fig 1
. If test light is on, go to next step. If test light is off, repair open in battery feed circuit to horn relay. See WIRING DIAGRAMS
.
- Turn ignition off. Disconnect BCM J3 connector (Brown). Using a DVOM, check for voltage between horn relay connector terminals No. 28 and 1540. If volage is not present, repair open or poor connection in Black wire between horn relay connector and BCM. If voltage is present, repair short to ground in Black wire between horn relay and BCM or between horn relay and horn switch. See WIRING DIAGRAMS
.
Courtesy of GENERAL MOTORS CORP.