Faulty master cylinder pressure sensor; Damaged or corroded sensor wiring or connector; Contaminated or degraded brake fluid affecting sensor readings; Air trapped in the master cylinder or hydraulic system; Failed ABS control module or internal sensor circuit; Low brake fluid level or a hydraulic leak; Mechanical binding or wear inside the master cylinder

DTC codes / C01xx · Brakes, steering and suspension / C0131

C0131Master Cylinder Pressure Sensor Range/Performance

Q: What does code C0131 mean?

Master Cylinder Pressure Sensor Range/Performance. C0131 means the antilock braking system (ABS) module has detected that the master cylinder pressure sensor signal is outside its expected range or is not performing as designed. The computer compares the sensor's voltage against known pressure values and flags the code when the signal is implausible, erratic, or stuck within a key-on or driving cycle.

C0131 means the antilock braking system (ABS) module has detected that the master cylinder pressure sensor signal is outside its expected range or is not performing as designed. The computer compares the sensor's voltage against known pressure values and flags the code when the signal is implausible, erratic, or stuck within a key-on or driving cycle.

SystemChassis

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaBrakes, steering and suspension

Symptoms you may notice

ABS warning light illuminated on the dashboard
Traction control or stability control warning light also on
Often no symptoms besides the warning light
Reduced or disabled ABS and traction control functions
Brake pedal feel that seems normal but ABS does not activate during hard stops
Intermittent warning light that comes and goes with temperature or vibration

Common causes, most likely first

Faulty master cylinder pressure sensor
Damaged or corroded sensor wiring or connector
Contaminated or degraded brake fluid affecting sensor readings
Air trapped in the master cylinder or hydraulic system
Failed ABS control module or internal sensor circuit
Low brake fluid level or a hydraulic leak
Mechanical binding or wear inside the master cylinder

How to diagnose and fix it

Check brake fluid level and inspect for leaks around the master cylinder and lines
Scan all modules for stored and pending codes, and record freeze-frame data if available
Inspect the pressure sensor connector and wiring for corrosion, chafing, or loose pins
Test the sensor signal with a scan tool while applying brake pressure to verify linear voltage output
Perform a brake fluid flush and bleed the system if fluid is dark or contaminated
Replace the master cylinder pressure sensor if signal testing confirms it is out of range
Clear codes and road-test the vehicle to confirm the repair and verify ABS operation

What the pressure sensor code hides

A low brake fluid level or a small leak can set C0131 because the sensor reads pressure outside the expected range for the pedal position.
Corroded pins at the sensor connector often mimic a failed sensor, so always wiggle-test the harness while watching live data before replacing parts.
Air in the hydraulic system after a poor bleed job can cause erratic pressure readings that trigger this code without any hard part failure.
The ABS module may set C0131 as a companion code when the wheel speed sensors or steering angle sensor are faulty, so check for other codes first.
Replacing the sensor without checking brake fluid condition and bleeding the system can lead to a repeat code and wasted expense.

Can I keep driving with C0131?

The vehicle remains safe to drive under normal conditions because the base brakes still work, but ABS and traction control may be disabled. Avoid hard braking or slippery road conditions until the fault is repaired, and address any low brake fluid level immediately.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.