GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 Vibe - FWD 🢒 DTC 🢒 DTC C0274

Circuit Description

The pump motor relay is part of the electronic brake control module (EBCM) on vehicles without traction control. The pump motor relay is located in the Antilock Brake System (ABS) relay block on vehicles with traction control. The EBCM turns ON and OFF the pump motor relay as deemed necessary in order to activate the pump motor. The pump motor modulates brake hydraulic pressure during an ABS stop.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0274 ABS Motor Relay Shorted

Conditions for Running the DTC

DTC C0274 can be set anytime the ignition switch is in the ON position.

Conditions for Setting the DTC

The EBCM detects a short in the pump motor circuitry.

Action Taken When the DTC Sets
    • The ABS is disabled.
    • The ABS warning indicator turns ON.
    • The traction control and vehicle stability control (VSC) is disabled, if equipped.
    • The VSC warning indicator turns ON, if equipped.

Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Diagnostic Aids

Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.

The following are possible causes of the malfunction:

    • An open, high resistance, or short to ground in the battery positive voltage circuit
    • An open or high resistance in the motor ground circuit
    • An internal EBCM malfunction

If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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

  1. This step determines if the DTC is current.

    2.

  2. This step tests the relay circuits between the ABS relay block and the EBCM for an open, high resistance, or short to ground.

    3.

  3. This step tests the battery positive voltage circuit for an open, high resistance, or short to ground.

    4.

  4. This step tests the motor ground circuit for an open or high resistance.

Step

Action

Values

Yes

No

Schematic Reference: Antilock Brake System Schematics

Connector End View Reference: Antilock Brake System Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Use the scan tool in order to clear the DTCs.
  4. Using the scan tool, cycle the pump motor in the Special Functions menu.
  5. Read the DTCs.

Does the DTC reset?

--

Go to Step 3

Go to Diagnostic Aids

3

Is the vehicle equipped with the traction control system?

--

Go to Step 4

Go to Step 5

4
  1. Turn OFF the ignition.
  2. Remove the Antilock Brake System (ABS) motor relay.
  3. Turn ON the ignition.
  4. Measure the voltage between the battery positive voltage terminal of the ABS motor relay and a good ground.

Does the voltage measure as specified?

10-14 V

Go to Step 6

Go to Step 7

5
  1. Turn OFF the ignition.
  2. Disconnect the electronic brake control module (EBCM) harness connector.
  3. Measure the voltage between the battery positive voltage circuits of the EBCM and a good ground.

Does the voltage measure as specified?

10-14 V

Go to Step 8

Go to Step 9

6

Test the relay circuits between the ABS relay block and the EBCM for the following:

    • An open
    • High resistance
    • Short to ground

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 11

7

Test the battery positive voltage circuit for the following:

    • An open
    • High resistance
    • Short to ground

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

8

Measure the resistance between the EBCM ground circuits and a good ground.

Does the resistance measure as specified?

Below 1 ohms

Go to Step 13

Go to Step 10

9

Locate and repair the following in the battery positive voltage circuit.

    • An open
    • High resistance
    • Short to ground

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

--

10

Locate and repair the open or high resistance in the motor ground circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

--

11

Replace the ABS motor relay.

Did you complete the replacement?

--

Go to Step 14

--

12

Replace the ABS cutoff relay.

Did you complete the replacement?

--

Go to Step 14

--

13

Replace the brake pressure modulator valve (BPMV). Refer to Brake Pressure Modulator Valve Assembly Replacement .

Did you complete the replacement?

--

Go to Step 14

--

14
  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 2

System OK