For 1990-2009 cars

### Circuit Description

The instrument panel cluster (IPC) turns the ABS indicator on during the IPC bulb check for approximately 3 seconds when the ignition switch is turned to the ON position. If the electronic brake control module (EBCM) sets a diagnostic trouble code (DTC) the EBCM sends a class 2 message to the body control module (BCM) and the BCM sends a class 2 message to the IPC to command the antilock brake system (ABS) indicator ON.

### Diagnostic Aids

• | It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.

• | Thoroughly inspect any circuitry that may be causing the complaint for the following conditions:

- | Backed out terminals

- | Improper mating

- | Broken locks

- | Improperly formed or damaged terminals

- | Poor terminal-to-wiring connections

- | Physical damage to the wiring harness

• | The following conditions may cause an intermittent malfunction:

- | A poor connection

- | Rubbed-through wire insulation

- | A broken wire inside the insulation

• | If an intermittent malfunction exists refer to Inducing Intermittent Fault Conditions in Wiring Systems.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Confirm if the scan tool can turn ON and OFF all indicator lamps on the instrument cluster.

1. Verify if the circuits going to the instrument cluster or the cluster is at fault.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: refer to Antilock Brake System Connector End Views or Displays and Gages Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2 |

1. Using a scan tool, select the brake control module (BCM), Special Functions mode.
2. Select Output Control, Solenoid Test.
3. Select the antilock brake system (ABS) Telltale Indicator.
4. In the ABS Telltale test mode you can turn the instrument panel indicators ON or OFF.

All indicators will turn ON when commanded on.

Does the ABS indicator turn on then OFF?

Go to Step 3

Go to Step 4

3 | Replace the electronic brake control module (EBCM). Refer to Control Module References in Computer/Integrating Systems. Is the replacement complete? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | --
4 |

1. Disconnect the instrument cluster and connect a test light across the appropriate power and ground terminals.
2. With the test light OFF, repair the open in power or ground circuit to cluster
3. With the test light ON, check the connector for poor connection to cluster.
4. If OK, replace the instrument cluster. Refer to Control Module References in Computer/Integrating Systems.

Is the instrument cluster replacement complete?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

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