For 1990-2009 cars

### 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.

2. The symptom list in Symptoms will determine the correct diagnostic procedure to use.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Battery Inspection/Test? | Go to Step 2 | Go to Battery Inspection/Test
2 | Install a scan tool. Does the scan tool power up? | Go to Step 3 | Go to Scan Tool Does Not Power Up in Data Link Communications
3 |

1. Turn ON the ignition, with the engine OFF.
2. Attempt to communicate with the powertrain control module (PCM).

Does the scan tool communicate with the PCM?

Go to Step 4

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

4 |

1. Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules have DTCs set.
2. Record all of the displayed DTCs the DTC status and the module which set the DTC.

Does the scan tool display any DTCs?

Go to Step 5

Go to Symptoms - Engine Electrical

5 | Does the scan tool display any DTC beginning with "U"? | Go to Diagnostic Trouble Code (DTC) List in Data Link Communications | Go to Diagnostic Trouble Code (DTC) List