For 1990-2009 cars
ABS Components
Antilock Brake System Schematics

### Circuit Description

The Electronic Brake Control Module (EBCM) controls the operation of the amber ABS indicator lamp by means of a lamp driver relay.

The amber ABS indicator lamp is connected to the IG-COIL METER fuse through CKT 8B01. This circuit is hot in ON and START ignition switch positions.

When the lamp driver relay is in the OFF state (CKT 9U01 is open), the lamp driver relay grounds the amber ABS indicator lamp through CKT 6B01. This turns ON the amber ABS warning indicator.

When the EBCM commands OFF the ABS warning indicator, the EBCM turns ON the lamp driver relay by grounding CKT 9U01. This causes the lamp driver relay to open the path to ground in CKT 6B01, turning OFF the amber ABS warning indicator.

When the ignition switch is turned to the ON position, the EBCM turns ON the ABS indicator for 3 seconds for a bulb check. Whenever a malfunction is detected within the ABS system, the EBCM tuns ON the ABS indicator, notifying the driver that ABS needs to be serviced. If the EBCM commands the red BRAKE warning indicator ON due to an ABS malfunction that may degrade base braking operation and cannot do so, the ABS indicator will flash to indicate the serious nature of the problem.

### Diagnostic Aids

Thoroughly inspect any circuitry that may cause the intermittent 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

• | Short to ground between the lamp driver relay and the amber ABS indicator lamp (CKT 6B01)

• | Open circuit or high resistance between the EBCM and the lamp driver relay (CKT 9U01)

• | Open coil or constantly closed contacts of the lamp driver relay

Important: Zero the J 39200 test leads before making any resistance measurements. Refer to the J 39200 user's manual.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check
2 |

1. Turn the ignition switch to the OFF position.
2. Install a Scan Tool .
3. Turn the ignition switch to the ON position.

Do not start the engine.

4. Select Special Functions on the Scan Tool .
5. Select Lamp Test on the Scan Tool .
6. Use the Scan Tool in order to toggle the amber ABS warning indicator ON and OFF.

Did the amber ABS warning indicator toggle ON and OFF?

--

Go to Step 11

Go to Step 3

3 |

1. Disconnect the lamp driver relay.
2. Turn the ignition switch to the ON position.

Is the amber ABS warning indicator ON?

--

Go to Step 4

Go to Step 6

4 | Check CKT 6B01 for a short to ground and repair as necessary. Was there a problem found and corrected? | -- | Go to Step 13 | Go to Step 5
5 | Repair the Instrument Panel Cluster. Refer to Instrument Cluster, Cell 81, in Electrical Diagnosis. Is the repair complete? | -- | Go to Step 13 | --
6 |

1. Turn the ignition switch to the ON position.
2. Probe the lamp driver harness connector terminal 2 with a J 34730-2C connected to ground.

Did the test light turn ON?

--

Go to Step 7

Go to Step 12

7 |

1. Connect a J 34730-2C between the lamp driver relay harness connector terminals 2 and 5.
2. Use the Scan Tool in order to toggle the amber ABS warning indicator ON and OFF.

Did the test light toggle ON and OFF?

--

Go to Step 8

Go to Step 10

8 | Inspect for proper terminal contact at the lamp driver relay. Was there a problem found and corrected? | -- | Go to Step 13 | Go to Step 9
9 | Replace the lamp driver relay. Is the repair complete? | -- | Go to Step 13 | --
10 | Check CKT 9U01 for an open or high resistance condition. Was there a problem found and corrected? | -- | Go to Step 13 | Go to Step 11
11 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Is the repair complete? | -- | Go to Step 13 | --
12 | Check CKT 8B01 for an open or high resistance condition. Was there a problem found and corrected? | -- | Go to Step 13 | --
13 |

1. Reconnect the lamp driver relay.
2. Turn the ignition switch to the ON position and observe the ABS warning indicator.

Did the amber ABS warning indicator turn ON for 3 seconds and then turn OFF?

--

System OK

Go to Diagnostic System Check