GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC C0550

Circuit Description

This DTC identifies a problem in battery positive voltage or ground circuitry to the electronic brake control module (EBCM) or an EBCM internal malfunction.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0550 Electronic Control Unit (ECU) Performance

Conditions for Running the DTC
    • The ignition is ON.
    • The vehicle speed is greater than 20 km/h (13 mph).

Conditions for setting the DTC

The EBCM detects low battery voltage at the system relay or an internal malfunction.

Action Taken When the DTC Sets

If equipped, the following actions may occur.

    • The EBCM disables Antilock Brake System (ABS)/Traction Control System (TCS).
    • The Hydromax pump motor turns ON.
    • The ABS indicator turns ON.
    • The traction off indicator turns ON.
    • The brake warning indicator turns ON.
    • The service brake soon indicator turns ON.

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

Replace the EBCM if DTC C0550 continues to set intermittently and no problems with power or ground circuits or connections are identified.

Test Description

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

  1. A brake indicator signal circuit which is shorted to voltage not only causes the service brake soon indicator to be inoperative, but also may damage the EBCM.

    2.

  2. The EBCM must be replaced regardless of whether or not the brake indicator signal circuit is shorted to voltage. If the service brake soon indicator is inoperative after EBCM replacement, refer to Diagnostic System Check - Vehicle .

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

Does the DTC set?

Go to Step 3

Go to Diagnostic Aids

3
  1. Turn OFF the ignition.
  2. Disconnect the electronic brake control module (EBCM) harness connector.
  3. Connect a test lamp between each battery positive voltage circuit and a good ground, one at a time.

Does the test lamp illuminate when connected to each circuit?

Go to Step 4

Go to Step 5

4

Test the EBCM ground circuits for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 11

Go to Step 6

5

Repair the open or high resistance in the battery positive voltage circuits which did not illuminate the test lamp. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 11

--

6

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

Did you find and correct the condition?

Go to Step 11

Go to Step 7

7

  1. Reconnect the EBCM harness connector.
  2. Turn ON the ignition while observing the service brake soon indicator on the telltale circuit board.

Does the service brake soon indicator turn ON?

Go to Step 10

Go to Step 8

8

Important: If the fuse in the jumper wire opens when you perform this test, the brake indicator signal circuit is shorted to voltage. This condition must be repaired prior to EBCM replacement.

  1. Turn OFF the ignition.
  2. Disconnect the EBCM harness connector.
  3. Turn ON the ignition.
  4. Connect a fused jumper wire between the brake indicator signal circuit and a good ground. Refer to Using Fused Jumper Wires .

Does the service brake soon indicator turn ON?

Go to Step 10

Go to Step 9

9

Test the brake indicator signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 10

10

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

Did you complete the replacement?

Go to Step 11

--

11
  1. Use the scan tool in order to clear the DTCs.
  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