GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 Regal (China) 🢒 Body and Accessories 🢒 Stationary Windows 🢒 Diagnostic System Check - Automatic Day-Night Mirror

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.

    2.

  2. The presence of DTCs which begin with "U" indicate some of the modules are not communicating.

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 PCM and BCM on the class 2 circuit serial data circuit. (If using a Tech 2, obtain this information using the Class 2 Message Monitor feature.)

Does the scan tool communicate with the modules?

Go to Step 3

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

3
  1. Select the Display DTCs function for each module. (If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set.)
  2. Record all of the displayed DTCs, the DTC status, and the module which set the DTC.

Does the scan tool display any DTCs?

Go to Step 4

Go to Symptoms

4

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

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

Go to Step 5

5

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

For the 2.5L (LB8) engine go to Diagnostic Trouble Code (DTC) List/Type in Engine Controls

Go to Symptoms