GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 TopKick C-Series (Crew) C4/C5 🢒 Brakes 🢒 Air Antilock Brake System 🢒 Air ABS Indicator Always On

Circuit Description

The electronic brake control module (EBCM) sends a central area network (CAN) serial data message to the serial data gateway (SDG) module. The SDG module converts the CAN message to a class 2 serial data message and sends the message to the instrument panel cluster (IPC). The IPC interprets the class 2 message from the SDG module and commands the Antilock Brake System (ABS) indicator ON or OFF.

Diagnostic Aids

The malfunction must be present during diagnosis in order to prevent unnecessary parts replacement. Always begin diagnosis with Diagnostic System Check - Vehicle .

Test Description

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

  1. This step tests if the IPC is able to turn OFF the ABS indicator.

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn OFF the ignition for 5 seconds.
  2. Turn ON the ignition while observing the Antilock Brake System (ABS) indicator.

Does the ABS indicator illuminate for 3 seconds and then turn OFF?

Go to Diagnostic Aids

Go to Step 3

3

  1. Install a scan tool.
  2. Select the instrument panel cluster (IPC) Special Functions menu on the scan tool.
  3. Command the ABS Lamp OFF.

Does the ABS indicator turn OFF?

Go to Step 5

Go to Step 4

4

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

Did you complete the replacement?

Go to Step 6

--

5

Replace the electronic brake control module (EBCM). Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 6

--

6
  1. Turn OFF the ignition for 5 seconds.
  2. Turn ON the ignition while observing the ABS indicator.

Does the ABS indicator illuminate for 2 seconds and then turn OFF?

System OK

Go to Step 3