Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Verifies that the body control module (BCM) is providing ground to the horn relay.
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Tests for voltage at the battery positive voltage terminal of the horn relay coil.
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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.
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The horns need maximum current flow to operate properly. A high resistance, greater than 0.5 ohms, 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.
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The horn relay control circuit includes the horn slip ring and the horn switch. The horn slip ring and the horn switch must be tested for a high resistance, an open or a short to voltage when testing the relay control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Horns Diagnostic System Check? | Go to Step 2 | |
2 | Is the vehicle equipped with keyless entry (AU0)? | Go to Step 3 | Go to Step 4 |
3 |
Does the horn operate? | Go to Step 4 | Go to Step 5 |
4 | Depress the horn switch. Does the horn operate? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 6 |
Test the body control module (BCM) portion of the horn relay control circuit for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 14 | |
Does the test lamp illuminate? | Go to Step 7 | Go to Step 17 | |
7 |
Does the test lamp illuminate? | Go to Step 8 | Go to Step 18 |
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 9 | Go to Step 19 | |
9 | Momentarily connect a 15 amp fused jumper wire between the battery positive voltage circuit of the horn relay switch and the horn control circuit. Does the horn operate? | Go to Step 15 | Go to Step 10 |
10 | Reconnect the horn relay. Disconnect the horn connector. Connect a test lamp between the horn control circuit and a good ground. Depress and hold the horn switch. Does the test lamp illuminate? | Go to Step 11 | Go to Step 20 |
11 | Connect a test lamp between the horn control circuit and the horn ground circuit. Depress and hold the horn switch. Does the test lamp illuminate? | Go to Step 12 | Go to Step 21 |
12 | Inspect for poor connections at the horn. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 13 |
13 |
Does the horn operate? | Go to Step 16 | Go to Step 24 |
14 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 22 |
15 | Inspect for poor connections at the horn relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 23 |
Repair the high resistance in the horn control circuit or the horn ground circuit. A resistance as low as 0.5 ohms could cause operating problems with the horns. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 25 | -- | |
17 | Repair the open or high resistance in the battery positive voltage circuit of the horn relay coil. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 25 | -- |
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Important: The horn switch is part of the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement in SIR. To disable the SIR system refer to Disabling the SIR System in SIR. Repair the open or short to voltage in the horn relay control circuit. The horn relay control circuit includes the horn slip ring and the horn switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 25 | -- | |
19 | Repair the open or high resistance in the battery positive voltage circuit of the horn relay switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 25 | -- |
20 | Repair the open or high resistance in the horn control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 25 | -- |
21 | Repair the open or high resistance in the horn ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 25 | -- |
22 |
Important: Perform the BCM programming procedure when replacing the BCM. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the repair? | Go to Step 25 | -- |
23 | Replace the horn relay. Did you complete the replacement? | Go to Step 25 | -- |
24 | Replace the horn. Refer to Horn Replacement . Did you complete the replacement? | Go to Step 25 | -- |
25 | Operate the horn. Does the horn operate properly? | System OK | Go to Step 1 |
