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.
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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 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. 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. Do the horns operate? | -- | Go to Step 3 | Go to Step 5 |
3 |
Do the horns operate? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 4 |
Test the 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 21 | Go to Step 11 | |
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 14 | |
6 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 15 |
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 |
Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 17 |
10 |
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 Conditions and Poor Connections and Connector Repairs in Wiring Systems. 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 Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 20 |
Repair the high resistance in the horn control circuit or the horn ground circuit. (The horn control circuit includes the HORN fuse.) (A resistance as low as 0.5ohms could cause operating problems with the horns. Also, though unlikely, it is possible that both horns are defective.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. 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 and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | -- |
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 and Wiring Repairs in Wiring Systems. 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 and Wiring Repairs in Wiring Systems. 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 and Wiring Repairs in Wiring Systems. 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 and Wiring Repairs in Wiring Systems. 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 in Body Control Systems. Did you complete the repair? | -- | 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 |
