For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Theft Deterrent System Schematics Connector End View Reference: Theft Deterrent System Connector End Views DEFINITION: The horn does not sound when the CTD system is in alarm mode.
1 | Did you perform the Theft Deterrent Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Theft Deterrent
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 in Wiring Systems

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 in Horns
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. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
6 | Inspect for poor connections at the harness connector of the 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 8 | Go to Step 7
7 | Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Important: Perform the setup procedure for the BCM. 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