GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Vivant 🢒 Brakes 🢒 Antilock Brake System 🢒 ABS Indicator Inoperative

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 inoperative with no DTCs set.

    • Faulty ABS bulb/loose socket
    • I/P fuse open
    • Faulty cluster/lamp driver module
    • Faulty EBCM
    • Grounded circuit between the EBCM and the cluster

Step

Action

Value(s)

Yes

No

1

Did you perform a Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Disconnect the electronic brake control module (EBCM) harness from the EBCM.
  2. Turn the ignition switch ON.

Did the amber ABS lamp turn ON?

--

Go to Step 3

Go to Step 4

3

Replace the EBCM.

Did you complete the replacement?

--

System OK

--

4

Check the cluster fuse.

Is the fuse and terminal contact OK?

--

Go to Step 6

Go to Step 5

5
  1. Replace the open fuse and/or repair the loose terminals.
  2. Find the short, which caused the fuse to open, if applicable.

Did you find and correct the condition?

--

System OK

--

6
  1. Remove the amber ABS bulb from the cluster.
  2. Inspect for an open bulb filament or poor socket contact.

Was the socket and the bulb OK?

--

Go to Step 8

Go to Step 7

7

Replace the bulb/socket as needed.

Did you complete the replacement?

--

System OK

--

8
  1. Turn the ignition switch OFF.
  2. Verify the EBCM harness is still disconnected.
  3. Remove the cluster assembly from the instrument panel.
  4. Disconnect the white cluster harness connector from the cluster assembly.
  5. Turn the ignition switch ON.
  6. Connect a voltmeter to terminal B14 of the white cluster harness and then to body ground.

Does the voltage measure within the specified range?

Battery Voltage

Go to Step 10

Go to Step 9

9

Find and repair the source of low voltage on the cluster voltage supply terminal.

Did you find and correct the condition?

--

System OK

--

10
  1. Turn the ignition switch OFF.
  2. Disconnect the white cluster harness connector from the cluster assembly.
  3. Connect an ohmmeter between the white cluster harness terminal A14 and lamp driver module  (LDM) harness terminal 5.

Does the resistance measure less than the specified value?

2 ohms

Go to Step 12

Go to Step 11

11

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

Did you complete the repair?

--

System OK

--

12
  1. Turn the ignition switch OFF.
  2. Verify the LDM harness and the EBCM harness are still disconnected.
  3. Connect an ohmmeter to the EBCM harness terminal B8 and then to body ground.

Does the resistance measure OL, open circuit?

--

Go to Step 14

Go to Step 13

13

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

Did you find and correct the condition?

--

System OK

--

14

Replace the LDM.

Did you complete the replacement?

--

System OK

Go to Step 15

15

Replace the cluster assembly.

Did you complete the replacement?

--

System OK

--