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) |
Conditions for Running the DTC
| • | The body control system voltage is between 9.0 and 16.0 volts. |
| • | The BCM commands the horn relay on. |
Conditions for Setting the DTC
The BCM will set DTC 7 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 7 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 Body Control System. Refer to On-Board Diagnostic Features in Body Control System.
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.
-
Tests for voltage at the coil side of the horn relay. The HORN fuse supplies power to the coil side of the horn relay.
-
Tests if ground is constantly being applied to the horn relay.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Horn Schematics | |||
1 | Did you perform the Horns Diagnostic System Check? | Go to Step 2 | |
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 |
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 replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |
