For 1990-2009 cars

### Circuit Description

The instrument panel cluster (IPC) illuminates the ABS indicator by supplying ground to the lamp. The electronic brake control module (EBCM) sends class 2 serial data messages to the IPC, in order to command the indicator ON or OFF.

### Diagnostic Aids

The malfunction must be present during diagnosis in order to prevent unnecessary parts replacement. Always begin diagnosis with Diagnostic System Check - Vehicle .

### Test Description

The number below refers to the step number on the diagnostic table.

1. This step tests if the IPC is able to turn OFF the ABS indicator.

Step | Action | Yes | No
--- | --- | --- | ---
Important: After a DTC is cleared and the ignition is ON, the ABS indicator may remain ON until the EBCM completes a power-up self test. This test concludes when the vehicle reaches a speed greater than 10 km/h (7 mph) and the wheel speeds are verified by the EBCM.
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn OFF the ignition for 5 seconds.
2. Turn ON the ignition while observing the Antilock Brake System (ABS) indicator.

Does the ABS indicator illuminate for 2 seconds, then turn OFF?

Go to Diagnostic Aids

Go to Step 3

3 |

1. Install a scan tool.
2. Select the instrument panel cluster (IPC) Special Functions menu on the scan tool.
3. Select Lamp Tests.
4. Command all of the IPC indicator lamps OFF.

Does the ABS indicator turn OFF?

Go to Step 5

Go to Step 4

4 | Replace the IPC. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | --
5 | Replace the electronic brake control module (EBCM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | --
6 |

1. Turn OFF the ignition for 5 seconds.
2. Turn ON the ignition while observing the ABS indicator.

Does the ABS indicator illuminate for 2 seconds, then turn OFF?

System OK

Go to Step 3