GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 TrailBlazer - 2WD 🢒 Accessories 🢒 Entertainment 🢒 Diagnostic System Check - Entertainment System

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.

    First design uses a class 2 amplifier, 2nd design uses a non-class 2 amplifier.

    2.

  2. 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
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.

Does the scan tool power up?

Go to Step 2

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

2

Attempt to establish communication with the following:

    • Radio
    • Amplifier (1st design only), refer to Radio/Audio System Description and Operation for explanation of designs.
    • Body control module (BCM)
    • Auxiliary HVAC control module
    • Digital Radio Receiver (DRR)

Does the scan tool communicate with the radio, amplifier, BCM, auxiliary HVAC control module, and DRR?

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 following display DTCs function on the scan tool:

    • Radio
    • Amplifier (1st design only)
    • Body control module (BCM)
    • Auxiliary HVAC control module
    • Digital Radio Receiver (DRR)

Does the scan tool display any DTCs?

Go to Step 5

Go to Symptoms - Entertainment

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 B1000?

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

Go to Step 7

7

Does the scan tool display DTC B1327?

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

Go to Diagnostic Trouble Code (DTC) List