GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The electronic brake control module (EBCM) illuminates the service brake soon indicator by applying ground to the lamp.

Test Description

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

  1. This step tests if the EBCM is applying ground to the brake indicator signal circuit.

  2. This step tests for a short to ground in the brake indicator signal circuit by substituting the telltale circuit board with a test lamp.

Step

Action

Yes

No

Schematic Reference: Hydraulic Brake Schematics

Important: After DTC C0272 is cleared and the ignition is ON, the service brake soon indicator may remain ON until the vehicle is operated at a speed greater than 10 km/h (6 mph).

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Turn ON the ignition while observing the service brake soon indicator.

Does the service brake soon indicator illuminate for 3 seconds and then turn OFF?

Go to Testing for Electrical Intermittents

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the electronic brake control module (EBCM) harness connector.
  3. Turn ON the ignition.

Does the service brake soon indicator illuminate?

Go to Step 4

Go to Step 7

4

  1. Disconnect from the telltale circuit board, the harness connector containing the brake indicator signal circuit.
  2. At the telltale circuit board harness connector, connect a test lamp between the ignition 3 voltage circuit and the brake indicator signal circuit.
  3. Turn ON the ignition.

Does the test lamp illuminate?

Go to Step 5

Go to Step 6

5

Repair the short to ground in the brake indicator signal circuit. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 8

--

6

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

Did you complete the replacement?

Go to Step 8

--

7

Replace the EBCM. Refer to Control Module References .

Did you complete the replacement?

Go to Step 8

--

8

Turn ON the ignition while observing the service brake soon indicator.

Does the service brake soon indicator illuminate for 3 seconds and then turn OFF?

System OK

Go to Step 3