GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 HUMMER 🢒 2009 🢒 H2 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0131

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC C0131 00: ABS/TCS System Pressure Circuit Malfunction

DTC C0131 09: ABS/TCS Pressure Circuit Rate of Change Above Threshold

DTC C0131 0A: ABS/TCS Pressure Circuit Rate of Change Below Threshold

Circuit/System Description

The ABS pump motor and accumulator operates the ABS and base brake power assist systems. Pressurized brake fluid is stored in the accumulator and used for ABS and base brake power assist functions. An accumulator pressure sensor located internally in the electronic brake control module (EBCM) monitors the accumulator pressure. If accumulator pressure becomes too low, the ABS pump motor is commanded ON.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC
    • The accumulator internal power supply is out of range.
    • The accumulator pressure sensor value changes more than 15 MPa in 0.08 second.
    • The accumulator pressure signal fails to change at least 0.12 MPa during the accumulator pressure test.
    • The EBCM detects that the accumulator pressure signal is too low when the vehicle is driven.

Action Taken When the DTC Sets
    • The EBCM disables the Antilock Brake System (ABS)/Traction Control System (TCS)/Vehicle Stability Enhancement System (VSES) for the duration of the ignition cycle.
    • A DIC message and/or a warning message may be displayed.

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

Diagnostic Aids

The accumulator pressure sensor is located internally in the BPMV and is not serviceable.

Reference Information

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

Important: If present, diagnose DTC C0110 or C0201 before DTC C0131. An inoperative ABS motor or control can cause DTC C0131 to set.

Important:  It is recommended that the defective components be replaced, and not the complete brake master cylinder assembly.

  1. Cycle the ignition from OFF to ON. Observe the accumulator pressure data parameter on the scan tool. Fully apply and release the brake pedal once, the accumulator pressure should hold steady above 16.7 MPa.
    2. ⇒If the accumulator pressure data parameter does not hold steady above 16.7 MPa, replace the accumulator.
  2. Wait 60 seconds without depressing the pedal. The pump motor should not turn on.
    3. ⇒ If the ABS pump motor turns ON and OFF several times, replace the EBCM/brake pressure modulator valve (BPMV) assembly.
  3. Cycle the ignition from OFF to ON. Apply and release the brake pedal continuously. The accumulator pressure should not be below 14.9 for 100 seconds consecutively.
    4. ⇒If the accumulator pressure stays below 14.9 MPa for 100 seconds, replace the EBCM/BPMV assembly.
  4. Test drive the vehicle and observe the accumulator pressure data parameter while driving. The accumulator should not fluctuate rapidly.
    5. ⇒ If the accumulator pressure fluctuates rapidly replace the EBCM/BPMV assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure

Control Module References for EBCM and BPMV replacement, setup, and programming