GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Tracker - 4WD 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C1242 or C1243

Circuit Description

The pump motor is an integral part of the Brake Pressure Modulator Valve (BPMV). The electronic brake control relay supplies power to the solenoid valves and pump motor. The electronic brake control relay, located in the EBCM, is activated whenever the ignition switch is in the ON position and no malfunctions are present. The electronic brake control relay remains engaged until the ignition switch is turned OFF or a DTC which disables the ABS is set.

Conditions for Running the DTC

C1242

    • The switched system battery 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
    • ABS is disabled.
    • The ABS warning indicator turns ON.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.
    • 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF.

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:

    • The pump motor internals have an open.
    • The pump motor circuit is open.
    • The pump is binding.

The pump motor is an integral part of the BPMV and is not serviced separately.

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

Test Description

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

  1. This step uses the scan tool to test if the pump motor can be commanded ON and OFF.

    2.

  2. This step verifies the resistance of the pump motor.

Step

Action

Value(s)

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the A Diagnostic System Check - ABS?

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Go to Step 2

Go to Diagnostic System Check - ABS

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With the scan tool, command the pump motor ON and OFF. This is done with the Pump Motor Test located in ABS Special Functions.

Does the pump motor turn ON and OFF with each command?

--

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Remove the EBCM from the BPMV.
  3. Measure the resistance between the pump motor control circuits.

Does the resistance measure less than the specified value?

2 ohms

Go to Step 4

Go to Step 5

4

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

Did you complete the replacement?

--

Go to Step 6

--

5

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

Did you complete the replacement?

--

Go to Step 6

--

6
  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