GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 Eldorado 🢒 Body and Accessories 🢒 Keyless Entry 🢒 Diagnostic System Check - Horns

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.

    2.

  2. The symptoms list in Symptoms will determine the correct diagnostic procedure to use.

    3.

  3. The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.

    4.

  4. At this point you have determined all DTCs applicable to the horn system. Refer to Symptoms - Horns for further horn system diagnosis. Any other codes displayed from the listed modules do not apply to horns and should be diagnosed in the applicable section.

Step

Action

Yes

No

1

Install a scan tool.

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

2

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the body control module (BCM).

Does the scan tool communicate with the BCM?

Go to Step 3

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

3

Select the BCM display DTCs function on the scan tool.

Does the scan tool display any DTCs?

Go to Step 4

Go to Symptoms - Horns

4

Does the scan tool display any DTCs which begin with a "U"?

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

Go to Step 5

5

Does the scan tool display DTC B1552, B1556, or B1558?

Go to Diagnostic Trouble Code (DTC) List in Body Control System

Go to Symptoms - Horns