For 1990-2009 cars

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Install a scan tool.
2. Turn ON the ignition with the engine OFF.
3. With the scan tool, command the horn relay ON.

Does the horn sound?

--

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3 | Press the horn switch on the steering wheel. Does the horn sound? | -- | Go to Step 4 | Go to Horns Inoperative
4 |

1. Disconnect the body control module (BCM) connector containing the horn relay control circuit.
2. With a fused jumper wire and appropriate terminal adapter, ground the horn relay control circuit.

Does the horn sound?

--

Go to Step 6

Go to Step 5

5 | Test the horn relay control circuit for an open or short to battery. Did you find and correct the condition? | -- | Go to Step 8 | Go to Testing for Intermittent Conditions and Poor Connections
6 | Inspect for poor connections at the harness connector of the BCM. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7
7 | Replace the BCM. Refer to Body Control Module Replacement for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 8 | --
8 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 3