For 1990-2009 cars

### Diagnostic Aids

• | An intermittent malfunction in the electronic system may be very difficult to detect and to accurately diagnose. The EBCM tests for different malfunctions under different vehicle conditions. For this reason, a thorough test drive is often needed in order to repeat a malfunction. If the system malfunction is not repeated during the test drive, a good description of the complaint may be very useful in locating an intermittent malfunction. Faulty electrical connections or wiring cause most intermittent problems. When an intermittent condition is suspected, check the suspect circuits for the following conditions:

- | Poor mating of connector halves or backed out terminals

- | Improperly formed or damaged terminals

- | Wire chafing

- | Poor wire to terminal connections

- | Dirty or corroded terminals

- | Damage to connector bodies

• | If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. Perform a thorough inspection of all related wiring and connectors pertaining to the history DTC stored. Refer to General Electrical Diagnosis in Wiring Systems.

### 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.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Antilock Brake System Schematics
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 EBCM.

Does the scan tool communicate with the EBCM?

Go to Step 3

Go to Scan Tool Does Not Communicate with Electronic Brake Control Module in Data Link Communications

3 | Select the ABS display DTCs function on the scan tool. Does the scan tool display any DTCs? | Go to Diagnostic Trouble Code (DTC) List | Go to Symptoms - Antilock Brake System