GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C-Series Medium Duty Truck B7 🢒 Brakes 🢒 Antilock Brake System 🢒 ABS Indicator Inoperative

Circuit Description

The EBCM illuminates the ABS indicator by supplying ground to the lamp. When the ABS indicator is commanded on, the feedback voltage to the EBCM from the ABS indicator failure control circuit is low. The ABS indicator also illuminates if the brake lamp relay control circuit is open.

Diagnostic Aids

Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to the following:

    •  Testing for Electrical Intermittents
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs
    •  Connector Repairs

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step simulates the EBCM commanding the ABS indicator ON.

    2.

  2. This step tests the ABS indicator circuitry by substituting the IPC and the ABS indicator lamp with a test lamp.

Step

Action

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the ABS Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Turn OFF the ignition for 5 seconds.
  2. Turn ON the ignition while observing the ABS indicator.

Does the ABS indicator illuminate?

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect from the EBCM, the 24-way EBCM harness connector.
  3. Use a fused jumper wire and a connector adapter test kit in order to connect the ABS indicator failure control circuit to a good ground.
  4. Turn ON the ignition.

Does the ABS indicator illuminate?

Go to Step 7

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Reconnect the 24-way EBCM harness connector.
  3. Disconnect from the instrument panel cluster, the harness connector containing the ABS indicator failure control circuit. Refer to Instrument Cluster Replacement in Instrument Panel, Gages, and Console.
  4. Connect a test lamp between the ignition 1 voltage circuit and the ABS indicator failure control circuit.
  5. Turn ON the ignition.

Does the test lamp illuminate?

Go to Step 6

Go to Step 5

5

Repair the open in the ABS indicator failure control circuit. Refer to Wiring Repairs in Wiring Repairs.

Did you complete the repair?

Go to Step 11

--

6

Inspect the ABS indicator lamp for an open filament.

Did you find and correct the condition?

Go to Step 11

Go to Step 8

7

Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 9

9

Replace the instrument panel cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gages, and Console.

Did you complete the replacement?

Go to Step 11

--

10

Important: Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure and the Trim Level Calibration procedure.

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

Did you complete the replacement?

Go to Step 11

--

11
  1. Turn OFF the ignition for 5 seconds.
  2. Turn ON the ignition while observing the ABS indicator.

Does the ABS indicator illuminate?

System OK

Go to Step 3