GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Aveo 🢒 Brakes 🢒 Antilock Brake System 🢒 ABS Indicator Always On

Circuit Description

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

Battery voltage is supplied to the I/P cluster terminal 17, and the electronic brake control module terminal 4 when the ignition switch is turned ON. EBCM terminals 9 and 25 are hot at all times.

The default state is for the lamp driver module 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 turn ON the ABS warning lamp for 3 seconds for a bulb check.

Whenever a malfunction is detected within the ABS system, the EBCM turn 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 - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn the ignition switch OFF.
  2. Disconnect the electronic brake control module (EBCM) harness from the EBCM.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a fused jumper wire between terminal 16 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. Refer to Brake Pressure Modulator Valve Assembly Replacement .

Did you complete the replacement?

--

System OK

--

4
  1. Turn the ignition switch OFF.
  2. Remove the cluster assembly from the I/P.
  3. Disconnect the 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 terminal A2 and then to body ground.

Is the resistance as specified?

OL (open circuit)

Go to Step 6

Go to Step 5

5

Find and repair the short to ground between the I/P harness and the LDM harness.

Did you find and correct the condition?

--

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 5 of the LDM harness and then to EBCM harness terminal 16.

Was the resistance measured less than the specific value?

2 ohms

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

--

9

Replace the cluster assembly. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

--

System OK

--