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

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. DTCs from all of the modules listed must be retrieved. The symptom 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.

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 Power Up in Data Link Communications

2

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the following Control Modules:
    3. • Powertrain Control Module (PCM)
    • Body Control Module (BCM)
    • Instrument Cluster (IPC)

Does the scan tool communicate with the Powertrain Control Module (PCM), Body Control module (BCM), or the Instrument Cluster (IPC)?

Go to Step 3

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

3

Important: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.

  1. Access the Class 2 Power Mode in the Diagnostic Circuit Check in the BCM, PCM, and IPC inputs data display lists.
  2. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter.

Does the ignition switch parameter reading match the ignition switch position for all switch positions in each control module?

Go to Step 4

Go to Power Mode Mismatch in Body Control System

4

Select one of the following control modules to display DTC function on the scan tool:

    • Powertrain Control Module (PCM)
    • Body Control Module (BCM)
    • Instrument Cluster (IPC)

Does the scan tool display any DTCs?

Go to Step 5

Go to Symptoms - Lighting Systems

5

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 6

6

Does the scan tool display DTC B1552, B1556, B1558, or B1981?

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

Go to Step 7

7

Does the scan tool display DTC B1557?

Go to Diagnostic Trouble Code (DTC) List in Instrument Panel, Gages and Console

Go to Step 8

8

Does the scan tool display DTC P1820, P1822, P1823, or P1825?

Go to Diagnostic Trouble Code (DTC) List/Type in Automatic Transaxle-4T80-E

Go to Step 9

9

Does the scan tool display DTC B1982, B1983, B1910, or B1911?

Go to Diagnostic Trouble Code (DTC) List in Engine Electrical

Go to Diagnostic Trouble Code (DTC) List .