GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Inspect the vehicle for the UA6 theft deterrent option.

Is the vehicle equipped with the UA6 theft deterrent option?

--

Go to Step 2

Go to Step 3

2

Did you perform the Body Control Module (BCM) Diagnostic System Check?

--

Go to Step 3

Go to Diagnostic System Check - Body Control System in Body Control Systems

3

Remove the horn relay.

Do the horns stop sounding?

--

Go to Step 4

Go to Step 13

4

Connect a test lamp between the horn relay terminals CKT 740 and CKT 28. Refer to Fuse Block Details in Electrical Diagnosis for terminal location.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 7

5

  1. Leave the test lamp connected.
  2. Disconnect the BCM connector C2.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 8

6

  1. Disconnect connector C201
  2. Connect a test lamp between the horn relay terminals CKT 740 and CKT 28.

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 10

7

Replace the horn relay. Refer to Horn Relay Replacement for service procedure.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

8

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

9

Repair the short to ground in CKT 28 between the BCM and the accessory wiring junction block or between the accessory wiring junction block and C201.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

10

  1. Disable the supplemental inflatable restraint (SIR) system. Refer to Disabling the SIR System and Enabling the SIR System for service procedure.
  2. Remove the horn switch from the steering wheel.
  3. Disconnect the spring loaded terminal of the horn switch leading to connector C201. Leave the switch ground connected.
  4. Connect a test lamp between B+ and the spring loaded terminal that leads toward the horn switch.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 12

11

Replace the horn switch. Refer to Horn Replacement for service procedure.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

12

Repair the short to ground in CKT 28 between the horn switch and C201.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

13

Disconnect the accessory wiring junction block connector C3.

Do the horns stop sounding?

--

Go to Step 14

Go to Step 15

14

Replace the accessory wiring junction block.

Is the repair complete

--

Go to Diagnostic System Check - Horns

--

15

Repair the short to B+ CKT 29 between the horn connector and the accessory wiring junction block.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--