GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2000 🢒 Catera 🢒 Body and Accessories 🢒 Cellular Communication 🢒 OnStar System Check

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 or a total malfunction of the class 2 serial data circuit. The specified procedure will determine the condition.

    2.

  2. The presence of DTC's which begin with "U" indicate some other system control module is 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 Vehicle Interface Unit (VIU).

Does the scan tool communicate with the (VIU)?

Go to Step 3

Go to DTC U1000 and DTC U1255 Class 2 Communication Malfunction in Data Link Communications

3

Select the Vehicle Interface Unit (VIU) display DTCs function on the scan tool.

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 Step 5

Go to Step 6

5

Does the scan tool display DTC U1500?

Go to Diagnostic Trouble Code (DTC) List/Type

Go to DTC U1000 and DTC U1255 Class 2 Communication Malfunction in Data Link Communications

6

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

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

Go to Step 7

7

Does the scan tool display DTC B1327 or B1328?

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

Go to Diagnostic Trouble Code (DTC) List/Type