Test Description
The number(s) below refer to the step number(s) 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 0.5ohms) 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 control circuit includes the horn slip ring and the horn switch. The 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 | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Horns Diagnostic System Check? | -- | Go to Step 2 | |
2 | Depress the horn switch. Does the horn operate? | -- | Go to Step 3 | Go to Step 5 |
3 |
Does the horn operate? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 4 |
Test the body control module 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 24 | Go to Step 13 | |
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 16 | |
6 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 17 |
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 18 | |
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. Does the horn operate? | -- | Go to Step 14 | Go to Step 9 |
9 | 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 10 | Go to Step 19 |
10 | 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 11 | Go to Step 20 |
11 | 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 24 | Go to Step 12 |
12 |
Does the horn operate? | -- | Go to Step 15 | Go to Step 23 |
13 | 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 24 | Go to Step 21 |
14 | 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 24 | Go to Step 22 |
Repair the high resistance in the horn control circuit or the horn ground circuit. (A resistance as low as 0.5ohms 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 24 | -- | |
16 | 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 24 | -- |
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 24 | -- | |
18 | 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 24 | -- |
19 | 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 24 | -- |
20 | 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 24 | -- |
21 |
Important: Perform the programming procedure for the BCM. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | -- | Go to Step 24 | -- |
22 | Replace the horn relay. Did you complete the replacement? | -- | Go to Step 24 | -- |
23 | Replace the horn. Refer to Horn Replacement . Did you complete the replacement? | -- | Go to Step 24 | -- |
24 | Operate the horn. Does the horn operate properly? | -- | System OK | Go to Step 1 |
