For 1990-2009 cars

### Test Description

The numbers 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 symptoms list in Symptoms will determine the correct diagnostic procedure to use.

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. The presence of DTCs B2734, B2960, B3031, or B3055 indicate a vehicle theft deterrent system problem.

5. At this point you have determined all DTCs applicable to the Theft Deterrent system. Refer to Symptoms for further Theft Deterrent diagnosis. Any other codes displayed from the listed modules do not apply to Theft Deterrent and should be diagnosed in their applicable section.

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 following modules:

• | Powertrain Control Module (PCM)

• | PASS-Key Module

Does the scan tool communicate with both of the listed control modules?

Go to Step 3

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

3 | Select the display DTC function on the scan tool for the following modules:

• | Powertrain Control Module (PCM)

• | PASS-Key Module

Does the scan tool display any DTCs?

Go to Step 4

Go to Step 6

4 | 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 5
5 | Does the scan tool display DTC B2734, B2960, B3031 or B3055? | Go to Diagnostic Trouble Code (DTC) List/Type | Go to Step 6
6 | Attempt to operate the vehicle courtesy lamps and the power door locks. Are the courtesy lamps and the power door locks operational? | Go to Step 7 | Go to Body Control Module Inoperative in Body Control Systems
7 | Check for Body Control Module (BCM) DTC's. Refer to Diagnostic Trouble Code (DTC) Displaying in Body Control Systems. Does the BCM sound and flash DTC 6? | Go to DTC 6 Theft Deterrent Relay Control Circuit Shorted | Go to Step 8
8 | Does the BCM display or sound any other DTC's? | Go to Diagnostic Trouble Code (DTC) List/Type | Go to Symptoms - Theft Deterrent