For 1990-2009 cars

### 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. 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 | 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 radio.

Does the scan tool communicate with the radio?

Go to Step 3

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

3 | 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 4
4 | Enter the BCM Diagnostic Mode. Refer to On-Board Diagnostic Features in Body Control Systems. Does the BCM enter the Diagnostic Mode? | Go to Symptoms | Go to Body Control Module Inoperative