01 How do driverless cars navigate without road markings? • 02 ECU Tuning 101: Everything You Need to Know • 03 The ABS Light That Changes How Your Brakes Behave Without W… • 04 The Benefits of Catalytic Converters in Vehicle Exhaust Sys… • 05 P0021 A camshaft postion - timing over-advanced or system p… • 06 Pros and Cons of Using a Mortgage Loan to Buy a Car: What Y… • 07 Don't Get Stranded! A Guide to Roll Starting, Starters, and… • 08 How to tell if your spark plugs are bad: Signs, symptoms, a… • 09 Is Your Car Engine Losing Oil Even Though There's No Leak? … • 10 How Leaking a Head Gasket Affects Engine Performance •

DTC codes / C05xx · Brakes, steering and suspension / C0544

C0544Brake Pressure Sensor B Circuit/Open

C0544 indicates that the anti-lock brake system (ABS) control module has detected an open circuit or abnormal voltage on the signal circuit for brake pressure sensor B, which is often the master cylinder pressure sensor or a secondary pressure sensor in the hydraulic unit. The module monitors the sensor's voltage and sets this code when the signal falls outside the expected range for the current brake pedal position and hydraulic pressure.

SystemChassis
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaBrakes, steering and suspension

Symptoms you may notice

  • Illumination of the ABS warning light, and often the traction control and stability control lights as well
  • A brake warning light may also turn on if the fault affects the electronic brake distribution function
  • Reduced or disabled ABS and traction control operation during emergency braking or slippery conditions
  • A soft or inconsistent brake pedal feel in some cases, though often the pedal feels normal
  • No noticeable symptoms besides the warning lights in many instances

Common causes, most likely first

  1. Damaged, corroded, or disconnected wiring or connector at the brake pressure sensor B
  2. Failed brake pressure sensor B itself, due to internal open circuit or contamination
  3. Open circuit or high resistance in the signal circuit between the sensor and the ABS control module
  4. Poor electrical connection at the ABS control module harness, often from water intrusion or terminal corrosion
  5. Low brake fluid level or air in the hydraulic system causing abnormal pressure readings
  6. Faulty ABS control module, though this is less common than sensor or wiring issues

How to diagnose and fix it

  1. Check brake fluid level and inspect for leaks in the hydraulic system, topping off or repairing as needed
  2. Visually inspect the brake pressure sensor B and its connector for corrosion, damage, or loose pins, and clean or repair as necessary
  3. Use a scan tool to read live data from the brake pressure sensor B and compare it to expected values while pressing the brake pedal
  4. Perform a voltage drop test on the sensor's signal and ground circuits to check for excessive resistance or an open circuit
  5. If wiring and connections are good, test the sensor's resistance and output signal according to the manufacturer's specifications, and replace the sensor if it is out of range
  6. Clear the code and perform a road test to verify the repair, ensuring the ABS and traction control systems operate correctly

What Most Techs Overlook on C0544

  • A common mistake is replacing the brake pressure sensor B without first checking the wiring harness for chafing or corrosion, especially where it routes near the master cylinder or ABS pump.
  • The code can be set by a low brake fluid level or air in the system, so always verify the hydraulic system before condemning electrical components.
  • On some vehicles, the brake pressure sensor B is integrated into the ABS hydraulic control unit and cannot be serviced separately, requiring replacement of the entire unit.
  • Intermittent opens can be caused by a poor ground connection at the ABS module or chassis, which may not show up in static tests and require wiggle testing while monitoring live data.
  • This code does not always mean the sensor has failed; a faulty ABS control module or a software issue can also set it, so follow the diagnostic flow before replacing parts.

Can I keep driving with C0544?

The vehicle remains drivable in most cases because the base brakes still function, but ABS and traction control are disabled, which increases stopping distance on slippery surfaces. Avoid hard braking or driving in low-traction conditions, and have the fault diagnosed promptly to restore full safety system operation.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage