GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C-Series Medium Duty Truck B7 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0286 or C086

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 ground circuit between EBCM and the electronic brake control lamp relay is open.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The EBCM detects high feedback voltage from the ABS indicator failure control circuit when the ABS indicator is commanded ON.

Action Taken When the DTC Sets

This information-only DTC is stored in EBCM memory until it is cleared by using the specified procedure.

Conditions for Clearing the DTC

The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.

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 number below refers to the step number on the diagnostic table.

  1. Damage may occur to the EBCM, the ABS indicator failure control circuit and the ABS indicator lamp relay if the ABS indicator failure control circuit is shorted to voltage.

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. Use a scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 5 seconds.
  3. Turn ON the ignition and observe the scan tool.

Does the DTC set?

Go to Step 3

Go to Diagnostic Aids

3
  1. Turn OFF the ignition.
  2. Disconnect the ABS indicator lamp relay.
  3. Turn ON the ignition.
  4. Use the scan tool in order to clear the DTC.
  5. Turn OFF the ignition for 5 seconds.
  6. Turn ON the ignition and observe the scan tool.

Does the DTC set?

Go to Step 4

Go to Step 6

4
  1. Turn OFF the ignition.
  2. 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.
  3. Turn ON the ignition.
  4. Use a scan tool in order to clear the DTC.
  5. Turn OFF the ignition for 5 seconds.
  6. Turn ON the ignition and observe the scan tool.

Does the DTC set?

Go to Step 5

Go to Step 7

5

Test the ABS indicator failure control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 8

6

Inspect for poor connections at the harness connector of the ABS indicator lamp relay. 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 12

Go to Step 9

7

Inspect for poor connections at the harness connector of the instrument panel cluster. 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 12

Go to Step 10

8

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 12

Go to Step 11

9

Replace the ABS indicator lamp relay.

Did you complete the replacement?

Go to Step 12

--

10

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

Did you complete the replacement?

Go to Step 12

--

11

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 12

--

12
  1. Use the scan tool in order to clear the DTC.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 3

System OK