GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The ABS indicator is controlled by the EBCM. The EBCM supplies the ground to the ABS indicator circuit to turn the indicator on. When the ABS indicator circuit is not grounded at the EBCM, the ABS indicator remains off. The EBCM harness connector contains a shorting bar for the ABS indicator circuit. When the EBCM connector is disconnected from the EBCM, the shorting bar shorts the ABS indicator terminal to ground turning on the indicator.

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 Testing for Intermittent Conditions and Poor Connections in Wiring Systems for further diagnosis.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step checks for an internal EBCM malfunction.

  2. This step checks for an open in the ABS indicator circuit.

Step

Action

Value(s)

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - ABS

2

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the EBCM connector C1.
  3. Install the J 39700 Universal Pinout Box using the J 39700-280 Cable Adapter to connector C1 only.
  4. Connect a fused jumper wire between terminals 21 and 19 of J 39700 .
  5. Turn the ignition switch to the ON position.

Does the ABS Indicator come on?

--

Go to Step 3

Go to Step 4

3

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Is the replacement complete?

--

Go to Step 7

--

4

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the Instrument Cluster connector.
  3. Using DMM, measure the resistance between terminals 21 of J 39700 and the Instrument Cluster harness connector terminal 1.

Is the resistance within the range specified in the value(s) column?

0-5ohms

Go to Step 6

Go to Step 5

5

Repair the ABS Indicator circuit for an open or high resistance. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 7

--

6

Suspect the Instrument Cluster. Refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gauges and Console.

Is the repair complete?

--

Go to Step 7

--

7

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2