For 1990-2009 cars

### Circuit Description

The vehicle horns are activated whenever ground is applied to the horn relay coil through circuit 28. Ground may be applied to the relay coil by either of the following methods:

• | The body control module (BCM) (with UA6 only)

• | The horn switch

### Conditions for Setting the DTC

The BCM detects a short to B+ or ground in circuit 28.

### Action Taken When the DTC Sets

• | The BCM sets the diagnostic trouble code DTC 7.

• | If circuit 28 is shorted to B+, the horns are inoperative.

• | If circuit 28 is shorted to ground, the horns will sound all the time.

### Conditions for Clearing the MIL/DTC

• | A short to B+ or ground in circuit 28 is no longer present between the BCM and the horn relay.

• | After the repairs are completed, refer to Diagnostic Trouble Code (DTC) Clearing in order to clear the DTC.

### Diagnostic Aids

Inspect for a short to B+ or ground in circuit 28.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Always perform the horns diagnostic system check before attempting to diagnose DTC 7.

2. Inspects for a short to B+ in circuit 28.

3. Inspects for a short to ground in circuit 28.

4. Circuit 28 includes the horn slip ring and the horn switch. The horn switch is part of the inflatable restraint steering wheel module. The slip ring and switch must be tested for a short to B+ when testing circuit 28. Refer to Circuit Testing and Wiring Repairs in Wiring Systems and Inflatable Restraint Steering Wheel Module Replacement in SIR.

5. Circuit 28 includes the horn slip ring and the horn switch. The horn switch is part of the inflatable restraint steering wheel module. The slip ring and switch must be tested for a short to ground when testing circuit 28. Refer to Circuit Testing and Wiring Repairs in Wiring Systems and Inflatable Restraint Steering Wheel Module Replacement in SIR.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the horns diagnostic system check? | -- | Go to Step 2 | Go to Diagnostic System Check - Horns
2 |

1. Turn OFF the ignition.
2. Disconnect the horn relay.
3. Disconnect the BCM connector C2.
4. Turn ON the ignition, with the engine OFF.
5. Connect a test lamp between the BCM harness connector C2 terminal D10 and a good ground.

Does the test lamp illuminate?

--

Go to Step 4

Go to Step 3

3 | Connect a test lamp between the BCM harness connector C2 terminal D10 and B+. Does the test lamp illuminate? | -- | Go to Step 5 | Go to Step 6
4 | 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 short to B+ in circuit 28. (Circuit 28 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 7

--

5 | 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 short to ground in circuit 28. (Circuit 28 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 7

--

6 | 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 7 | --
7 |

1. Clear the BCM DTCs. Refer to Diagnostic Trouble Code (DTC) Clearing in Body Control Systems.
2. Operate the vehicle within the conditions for setting the DTC.

Does the DTC reset?

--

Go to Step 2

System OK