GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Remove the horn relay.

Do the horns stop sounding?

--

Go to Step 2

Go to Step 6

2

Using a test light, frontprobe between the horn relay circuit 740 and circuit 28. Refer to Fuse Block Schematics for terminal location.

Does the test light illuminate?

--

Go to Step 3

Go to Step 7

3

  1. Leave the test light in the same location.
  2. Disconnect the Body Control Module (BCM) connector C1.

Does the test light illuminate?

--

Go to Step 4

Go to Step 8

4

  1. Disconnect inline connector C201.
  2. Using a test light, frontprobe between the horn relay terminals circuit 740 and circuit 28.

Does the test light illuminate?

--

Go to Step 9

Go to Step 5

5

  1. Disable the Supplemental Inflatable (SIR) System. Refer to Disabling the SIR System for service procedure.
  2. Remove the horn switch from the steering wheel.
  3. Disconnect spring loaded terminal of the horn switch leading to connector C201, leaving the switch ground connected.
  4. Using a test light, probe between B+ and the spring loaded terminal leading towards connector C201.

Does the test light illuminate?

--

Go to Step 10

Go to Step 11

6

Disconnect the underhood accessory wiring junction block connector C3.

Do the horns stop sounding?

--

Go to Step 12

Go to Step 13

7

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

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

8

  1. Replace the BCM. Refer to Body Control Module Replacement for service procedure.
  2. Perform the new BCM setup procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration for service procedure.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

9

Repair short to ground in circuit 28.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

10

Repair short to ground in circuit 28.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

11

The horn switch is part of the SIR steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement for service procedure.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

12

Replace the underhood accessory wiring junction block. Refer to Accessory Wiring Junction Block Replacement for service procedure.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

13

Repair short to B+ in circuit 29.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--