GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Yukon Denali 🢒 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 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. Retrieve any existing DTC's.

    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. Check for internal errors in Vehicle Interface Unit (VIU).

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 Vehicle Interface Unit (VIU)?

Go to Step 3

Go to DTC U1XXX Loss of XXX Communication 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 in Cellular Communications

4

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

Go to Scan Tool Does Not Power Up in Data Link Communications

Go to Step 5

5

Does the scan tool display DTC B1000, B1004, B1009, B2462, B2476 or U1500?

Go to Diagnostic Trouble Code (DTC) List/Type in Cellular Communications

Go to Symptoms in Cellular Communications