For 1990-2009 cars

### Circuit Description

The EBCM illuminates the ABS indicator by supplying ground to the lamp. When the ABS indicator is commanded on, the feedback voltage to the EBCM from the ABS indicator failure control circuit is low. The ABS indicator also illuminates if the brake lamp relay control circuit is open.

### Diagnostic Aids

Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to the following:

• | Testing for Electrical Intermittents

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Connector Repairs

### Test Description

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

1. This step tests if the ABS indicator lamp relay is applying ground to the ABS indicator lamp.

2. This step tests if the EBCM is applying ground to the ABS indicator lamp.

3. This step tests the ABS indicator failure control circuit for a short to ground by substituting the instrument panel cluster (IPC) and the ABS indicator lamp with a test lamp while leaving the EBCM disconnected.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Antilock Brake System Schematics
1 | Did you perform the ABS Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - ABS
2 |

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

Does the ABS indicator illuminate for 4 seconds and then turn OFF?

Go to Diagnostic Aids

Go to Step 3

3 |

1. Turn OFF the ignition.
2. Remove the ABS indicator lamp relay from the Relay Center.
3. Turn ON the ignition while observing the ABS indicator.

Does the ABS indicator illuminate for 4 seconds and then turn OFF?

Go to Step 6

Go to Step 4

4 |

1. Turn OFF the ignition.
2. Disconnect the 24-way EBCM harness connector.
3. Turn ON the ignition while observing the ABS indicator.

Does the ABS indicator illuminate?

Go to Step 5

Go to Step 12

5 |

1. Turn OFF the ignition.
2. Disconnect from the instrument panel cluster, the harness connector containing the ABS indicator failure control circuit. Refer to Instrument Cluster Replacement in Instrument Panel, Gages, and Console.
3. Connect a test lamp between the ignition 1 voltage circuit and the ABS indicator failure control circuit.
4. Turn ON the ignition.

Does the test lamp illuminate?

Go to Step 7

Go to Step 13

6 | At the ABS indicator lamp relay connector in the Relay Center, connect a test lamp between the ignition 1 voltage circuit and a good ground. Does the test lamp illuminate? | Go to Step 9 | Go to Step 8
7 | Repair the short to ground in the ABS indicator failure control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 16 | --
8 | Repair the open in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring systems. Did you complete the repair? | Go to Step 16 | --
9 | Connect a test lamp between battery positive voltage and the brake lamp relay control circuit. Does the test lamp illuminate? | Go to Step 11 | Go to Step 10
10 | Test the brake lamp relay control circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 16 | Go to Step 12
11 | Replace the ABS indicator lamp relay. Did you complete the replacement? | Go to Step 16 | --
12 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 16 | Go to Step 15
13 | Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 16 | Go to Step 14
14 | Replace the instrument panel cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gages, and Console. Did you complete the replacement? | Go to Step 16 | --
15 | Important: Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure and the Trim Level Calibration procedure. Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | Go to Step 16 | --
16 |

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

Does the ABS indicator illuminate for 4 seconds and then turn OFF?

System OK

Go to Step 3