GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The pump motor relay is part of the electronic brake control module (EBCM). The EBCM turns ON and OFF the pump motor relay as deemed necessary to activate the pump motor.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C1251 Pump Motor Performance

Conditions for Running the DTC

DTC C1251 can be set anytime the pump motor is actuated.

Conditions for Setting the DTC

The EBCM detects a stuck pump motor.

Action Taken When the DTC Sets

    • The Antilock Brake System (ABS) is disabled.
    • The ABS warning indicator turns ON.
    • The 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 or high resistance in the EBCM ground circuits
    • An internal EBCM malfunction

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

Test Description

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

  1. This step determines if the DTC is current.

Step

Action

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

Test the electronic brake control module (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 5

Go to Step 4

4

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

Did you complete the replacement?

Go to Step 5

--

5

  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