GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 TopKick C-Series (Crew) C6/C7/C8 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Trailer ABS Indicator Always On

Circuit Description

The electronic brake control module (EBCM) receives a signal from the trailer Antilock Brake System (ABS) module over the ignition 1 voltage circuit. The EBCM applies ground to the trailer ABS indicator control circuit in order to turn ON the TRAILER ABS indicator.

Test Description

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

  1. This step tests if the trailer is the cause of the indicator staying on. If the vehicle does not have a trailer go to step 3.

Step

Action

Yes

No

Schematic Reference: Air Antilock Brake System Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Disconnect the trailer from the vehicle.

Does the TRAILER Antilock Brake System (ABS) indicator turn OFF?

The problem is with the trailer. Refer to the trailer manufacturer.

Go to Step 3

3

Disconnect the electronic brake control module (EBCM).

Does the TRAILER ABS Indicator turn OFF?

Go to Step 6

Go to Step 4

4
  1. Disconnect from the telltale circuit board, the harness connector containing the trailer ABS indicator control circuit.
  2. Test the trailer ABS indicator control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 7

Go to Step 5

5

Replace the telltale circuit board. Refer to Telltale Circuit Board Replacement .

Did you complete the repair?

Go to Step 7

--

6

Replace the EBCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 7

--

7
  1. Turn OFF the ignition for 5 seconds.
  2. Turn ON the ignition while observing the TRAILER ABS Indicator.

Does the TRAILER ABS Indicator turn ON?

Go to Step 2

System OK