GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Epica 🢒 Brakes 🢒 Antilock Brake System 🢒 ABS Active Indicator Always On

Circuit Description

The electronic brake control module (EBCM) controls the operation of the amber antilock brake system (ABS) warning lamp by means of a lamp driver module contained within the cluster.

Battery voltage is supplied to the instrument panel (I/P) cluster terminal B14, and the EBCM terminal A11 when the ignition switch is turned ON. EBCM terminals A and B are hot at all times.

The default state is for the lamp driver module (LDM) to turn ON the amber ABS warning lamp, by supplying a ground path through the lamp driver module.

When the EBCM commands the ABS lamp OFF, the EBCM will ground the ABS warning lamp control circuit. This causes the lamp driver module to open the path to ground for the bulb.

When the ignition switch is turned to the ON position, the EBCM turns ON the ABS warning lamp for 3 seconds for a bulb check.

Whenever a malfunction is detected within the ABS system, the EBCM turns ON the ABS warning lamp, notifying the driver that the ABS needs to be serviced.

Diagnostic Aids

Typical causes of the ABS warning lamp ON with no DTCs set:

    • Grounded circuit between the cluster and the EBCM
    • Faulty cluster/lamp driver module
    • Faulty EBCM

Step

Action

Value(s)

Yes

No

1

Did you perform a Diagnostic System Check - ABS?

--

Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Turn the ignition switch OFF.
  2. Disconnect the electronic brake control module (EBCM) harness from the EBCM.
  3. Turn the ignition switch ON.
  4. Connect a fused jumper wire between terminal B8 of the EBCM harness and body ground.

Did the amber ABS lamp turn OFF?

--

Go to Step 3

Go to Step 4

3

Replace the EBCM.

Did you complete the replacement?

--

System OK

--

4
  1. Turn the ignition switch OFF.
  2. Remove the cluster assembly from the instrument panel (I/P).
  3. Disconnect the white cluster harness connector from the cluster assembly.
  4. Disconnect the lamp driver module (LDM) harness connector from the LDM.
  5. Connect an ohmmeter to cluster harness A14 and then to body ground.

Does the resistance measure OL, open circuit?

--

Go to Step 6

Go to Step 5

5

Find and repair the short to ground between the cluster harness and the LDM harness.

Did you find and complete the repair?

--

System OK

--

6
  1. Turn the ignition switch OFF.
  2. Disconnect the EBCM harness from the EBCM.
  3. Disconnect the LDM harness from the LDM.
  4. Connect an ohmmeter to terminal 3 of the LDM harness and then to EBCM harness terminal B8.

Does the resistance measure less than the specified value?

2ohms

Go to Step 8

Go to Step 7

7

Repair the open or high resistance between the LDM and the EBCM.

Did you find and correct the condition?

--

System OK

--

8

Replace the LDM.

Did you complete the replacement?

--

System OK

Go to Step 9

9

Replace the cluster assembly.

Did you complete the replacement?

--

System OK

--