LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1388 (Horn System) >> Diagnostic Information and Procedures >> Horns Inoperative >> Test Description

Test Description

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. 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.

  1. 4:  Verifies that the body control module (BCM) is providing ground to the horn relay.
  2. 5:  Tests for voltage at the battery positive voltage terminal of the horn relay coil.
  3. 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.
  4. 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.
  5. 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.
Horns Inoperative

Step Action Yes No
1 Did you perform the Horns Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - Horns 
2 Depress the horn switch.
Do the horns operate?		 Go to Step 3  Go to Step 5 
3
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the body control module (BCM) Horn Output ON and OFF.
Do the horns operate?		 Go to TESTING FOR INTERMITTENT AND POOR CONNECTIONS Go to Step 4 
4  Test the BCM portion of the horn relay control circuit for a high resistance or an open. Refer to CIRCUIT TESTING or WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 21  Go to Step 11 
5 
  1. Turn OFF the ignition.
  2. Disconnect the horn relay.
  3. Connect a test lamp between the battery positive voltage circuit of the horn relay coil and a good ground.
Does the test lamp illuminate?		 Go to Step 6  Go to Step 14 
6
  1. Connect a test lamp between the battery positive voltage circuit of the horn relay coil and the horn relay control circuit.
  2. Depress and hold the horn switch.
Does the test lamp illuminate?		 Go to Step 7  Go to Step 15 
7  Connect a test lamp between the battery positive voltage circuit of the horn relay switch and a good ground.
Does the test lamp illuminate?		 Go to Step 8  Go to Step 16 
8 Momentarily connect a 15 amp fused jumper wire between the battery positive voltage circuit of the horn relay switch and the horn control circuit.
Do the horns operate?		 Go to Step 12  Go to Step 9 
9
  1. Reconnect the horn relay.
  2. Disconnect either horn connector.
  3. Connect a test lamp between the horn control circuit and a good ground.
  4. Depress and hold the horn switch.
Does the test lamp illuminate?		 Go to Step 10  Go to Step 17 
10
  1. Connect a test lamp between the horn control circuit and the horn ground circuit.
  2. Depress and hold the horn switch.
Does the test lamp illuminate?		 Go to Step 13  Go to Step 18 
11 Inspect for poor connections at the harness connector of the BCM. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS .
Did you find and correct the condition?		 Go to Step 21  Go to Step 19 
12 Inspect for poor connections at the horn relay. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS .
Did you find and correct the condition?		 Go to Step 21  Go to Step 20 
13  Repair the high resistance in the horn control circuit or the horn ground circuit. Also, though unlikely, it is possible that both horns are defective. Refer to CIRCUIT TESTING or WIRING REPAIRS .
Did you complete the repair?		 Go to Step 21  -
14 Repair the open or high resistance in the battery positive voltage circuit of the horn relay coil. Refer to CIRCUIT TESTING or WIRING REPAIRS .
Did you complete the repair?		 Go to Step 21  -
15  Repair the open or short to voltage in the horn relay control circuit. The horn relay control circuit includes the horn switch. Refer to CIRCUIT TESTING or WIRING REPAIRS .
Did you complete the repair?		 Go to Step 21  -
16 Repair the open or high resistance in the battery positive voltage circuit of the horn relay switch. Refer to CIRCUIT TESTING or WIRING REPAIRS .
Did you complete the repair?		 Go to Step 21  -
17 Repair the open or high resistance in the horn control circuit. Refer to CIRCUIT TESTING or WIRING REPAIRS .
Did you complete the repair?		 Go to Step 21  -
18 Repair the open or high resistance in the horn ground circuit. Refer to CIRCUIT TESTING or WIRING REPAIRS .
Did you complete the repair?		 Go to Step 21  -
19
IMPORTANT: Perform the BCM programming procedure when replacing the BCM.
Replace the BCM. Refer to BODY CONTROL MODULE REPLACEMENT .Did you complete the replacement?		 Go to Step 21  -
20 Replace the horn relay.
Did you complete the replacement?		 Go to Step 21  -
21 Operate the horns.
Do the horns operate properly?		 System OK Go to Step 1 
scientia non olet · About LEMON Manuals