Circuit Description
The vehicle horn is activated whenever ground is applied to the horn relay coil through the horn relay control circuit. Ground may be applied by any of the following:
| • | The body control module (BCM) |
| • | The horn switch |
| • | The vehicle interface unit (VIU) |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC 007 Horn Relay Control Circuit
Conditions for Running the DTC
| • | The Body Control System voltage is between 9-16 volts. |
| • | The BCM commands the horn relay ON. |
Conditions for Setting the DTC
The BCM will set DTC 007 under either of the following conditions:
| • | The BCM detects a short to ground in the horn relay control circuit. |
| • | The BCM detects a short to voltage in the horn relay control circuit. |
Action Taken When the DTC Sets
| • | If the horn relay control circuit is shorted to ground, the horns will remain ON at all times. |
| • | If the horn relay control circuit is shorted to voltage, the horn will not operate from the horn switches or when energized from either the BCM or the VIU. |
| • | The BCM stores DTC 007 in memory. |
Conditions for Clearing the DTC
A DTC will clear when the fault is no longer present and the DTCs are cleared as described in Computer/Integrating Systems. Refer to On-Board Diagnostic Features in Computer/Integrating Systems.
Diagnostic Aids
| • | Inspect for a sticking horn pad and or switch. |
| • | Perform a visual inspection for loose or poor connections at all related components. |
| • | Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for voltage at the coil side of the horn relay. The HORN fuse supplies power to the coil side of the horn relay.
-
This step tests if ground is constantly being applied to the horn relay.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Horn Schematics | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 | Depress the horn switch. Do the horns operate properly? | Go to Diagnostic Aids | Go to Step 3 |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 10 | |
4 |
Does the test lamp turn ON and then OFF? | Go to Step 8 | Go to Step 5 |
Does the test lamp remain illuminated when the horn switch is released? | Go to Step 7 | Go to Step 6 | |
6 |
Important: The horn switch is part of the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement in SIR.
Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
7 |
Important: The horn switch is part of the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement in SIR.
Did find and correct the condition? | Go to Step 13 | Go to Step 9 |
8 | 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 13 | Go to Step 11 |
9 | Inspect for poor connections at the harness connector of the body control module (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 13 | Go to Step 12 |
10 | Repair the battery positive voltage circuit of the horn relay coil. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 13 | -- |
11 | Replace the horn relay. Did you complete the replacement? | Go to Step 13 | -- |
12 | Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |
