GM Service Manual Online
For 1990-2009 cars only

Test Description

The number(s) below refer to the step number(s) 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.

    Enabling the headlamps in this step verifies that a door module is not using an alternate path to ground through the switch illumination circuit.

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

  3. The presence of DTCs U1161, U1162, U1163 or U1170 indicate one or more of the door modules is not communicating on the power door serial data circuits.

  4. The presence of other DTCs which begin with "U" indicate some other system control 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. Turn ON the headlamp switch.
  3. Attempt to establish communication with:
  4. • Driver door module (DDM)
    • Powertrain control module (PCM)

Does the scan tool communicate with the listed modules?

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 on the scan tool.
  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?

Go to Step 4

Go to Power Mode Mismatch in Body Control System

4

Select the Driver Door Module display DTCs function on the scan tool.

Does the scan tool display any DTCs?

Go to Step 5

Go to Symptoms - Doors

5

Does the scan tool display DTCs U1161, U1162, U1163 or U1164?

Go to DTC U1161-U1163 or U1170

Go to Step 6

6

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

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

Go to Step 7

7

Does the scan tool display DTC B1000, B1004, B1007, or B1009?

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

Go to Step 8

8

Does the scan tool display DTC B1327 or B1328?

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

Go to Step 9

9

Does the scan tool display B0490?

Go to Diagnostic Trouble Code (DTC) List in HVAC-Automatic

Go to Step 10

10

Does the scan tool display B2757, B2762 or B2772?

Go to Scan Tool Data List in Seats

Go to Step 11

11

Does the scan too display any DTCs that begin with "P"?

Go to Diagnostic Trouble Code (DTC) Types in Engine Controls

Go to Diagnostic Trouble Code (DTC) List