GM Service Manual Online
For 1990-2009 cars only

Important: The following steps must be completed before using the symptom tables.

  1. Perform Diagnostic System Check - Horns before using the symptom tables in order to verify that all of the following are true:
  2. • There are no DTCs set.
    • The body control module (BCM) can communicate via the serial data link.
  3. Review the system operation in order to familiarize yourself with the system functions. Refer to Horns System Description and Operation .

Visual/Physical Inspection

Several of the symptom procedures ask for a careful visual/physical inspection. This step is extremely important, it could lead to correcting a problem without further checks and can save valuable time. These checks include the following:

    • Inspect for aftermarket devices which could affect the operation of the Horn System. Refer to Checking Aftermarket Accessories in Wiring Systems.
    • Inspect the easily accessible or visible system components and harness connectors for obvious damage or conditions which could cause the symptom.

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

    • Perform the following if the horns buzz or have a harsh tone:
       - Inspect for debris in the joints where the horns fasten to the vehicle.
       - Test the torque of the horn mounting hardware. The horn mounting hardware should be tightened to a torque of 10 N·m (7 lb ft).

Intermittents

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose a symptom that does not set a DTC:

    •  Horns Always On
    •  Horns Inoperative
    •  Horns Inoperative - One Horn
    •  Horns - Poor Tone