GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2002 🢒 Montana Ext. 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C1242 or C1243

Circuit Description

The system relay is energized when the ignition is ON. The system relay supplies voltage to the solenoid valves and the pump motor. This voltage is referred to as the system voltage.

The electronic brake control module (EBCM) controls each solenoid valve by grounding the solenoid.

The EBCM controls the pump motor by grounding the control circuit. The pump serves 2 purposes:

    • Transfers brake fluid from the brake calipers to the master cylinder reservoir during pressure decrease events.
    • Transfers brake fluid from the master cylinder reservoir to the brake calipers during pressure increase events.

Conditions for Running the DTC

C1242

    • The system voltage is greater than 8.0 volts.
    • The system relay is ON.
    • The pump motor is commanded OFF.

C1243

    • The pump motor is ON for at least 0.3 seconds.
    • The system relay is ON.

Conditions for Setting the DTC

C1242

The voltage across the pump motor is between 1.7 - 10.2 volts for 2 seconds.

C1243

The pump motor is stalled or turning slowly.

Action Taken When the DTC Sets

If equipped, the following actions occur:

    • The EBCM disables the ABS/TCS for the duration of the ignition cycle.
    • The DRP does not function optimally.
    • The ABS indicator turns ON.
    • The Traction Off indicator turns ON.
    • The message center displays the Service Traction System message.

Conditions for Clearing the DTC
    • The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
    • The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids

The pump motor is integral to the BPMV. The pump motor is not serviceable.

Test Description

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

  1. Tests the ability of the EBCM to control the pump motor. If the test lamp illuminates, the pump motor circuit within the EBCM is good.

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 ABS Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Use the scan tool in order to clear the DTCs.
  2. With the scan tool, perform the Automated Test.

Does the DTC reset?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3
  1. Remove the EBCM from the BPMV. Refer to Electronic Brake Control Module Replacement .
  2. Inspect the EBCM to BPMV connector for conditions which could cause an intermittent, such as damage, corrosion, poor terminal contact, or presence of brake fluid.

Is the connector OK and the cavity free of brake fluid?

Go to Step 5

Go to Step 4

4
  1. If connector corrosion or damage is evident, replace BPMV and/or EBCM as necessary.
  2. If brake fluid is present, replace both BPMV and EBCM. Refer to Brake Pressure Modulator Valve Replacement and Electronic Brake Control Module Replacement .

Did you complete the repair?

Go to Step 8

--

5

  1. Connect the EBCM harness to the EBCM with the BPMV still separated.
  2. Connect a test lamp between the pump motor circuits, internal EBCM side, using the J 35616 GM terminal test kit .
  3. With the scan tool, perform the Automated Bleed.

Does the test lamp illuminate?

Go to Step 7

Go to Step 6

6

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Did you complete the repair?

Go to Step 8

--

7

Replace the BPMV. Refer to Brake Pressure Modulator Valve Replacement .

Did you complete the repair?

Go to Step 8

--

8
  1. Use the scan tool in order to clear the DTCs.
  2. With the scan tool, perform the Automated Test.

Does the DTC reset?

Go to Step 2

System OK