What Does C1954 Mean?
The ABS/stability control module has detected that the master cylinder pressure sensor is electrically connected but producing irrational, erratic, or out-of-range readings that do not correlate with expected braking behavior. The sensor may be degraded, producing noisy signals, or stuck at an incorrect value. The module cannot trust the pressure data for brake-assist or stability control calculations. Warning lights will be illuminated.
Common Causes
35%
Degraded brake pressure sensor transducer producing noisy or drifting output
25%
Intermittent wiring connection causing signal noise or dropout
15%
Brake fluid contamination or air in the hydraulic system producing inconsistent pressure readings
15%
5V reference voltage fluctuation from the ABS module affecting sensor accuracy
10%
Electromagnetic interference from nearby components affecting the sensor signal
Diagnostic Steps
1
Monitor the brake pressure sensor PID in live data with the engine running and no brake pedal applied. The reading should be stable and near zero. Note any fluctuation, drift, or unexpected baseline offset.
2
Slowly press the brake pedal and observe the pressure reading — it should increase smoothly and proportionally with pedal effort. Look for erratic jumps, sudden drops, or failure to reach expected maximum pressure (typically 1500-2500 psi at full force).
3
Check the 5V reference voltage at the sensor connector with a precise multimeter. It should be stable at 5.00V +/- 0.05V. Fluctuating reference voltage will cause proportional errors in the pressure reading.
4
Wiggle the sensor connector and wiring harness while monitoring live data. Any change in the reading during the wiggle test indicates an intermittent connection that needs repair.
5
Inspect the brake fluid condition — contaminated or moisture-laden fluid can cause micro-bubbles under pressure, leading to inconsistent pressure sensor readings. Check the fluid's boiling point with a brake fluid tester.
6
If all electrical checks pass, replace the pressure sensor. These transducers can degrade over time, especially in the harsh engine bay environment.
Estimated Repair Cost
$100 - $550
Parts + labor, varies by vehicle and location
The ABS/stability control module has detected that the master cylinder pressure sensor is electrically connected but producing irrational, erratic, or out-of-range readings that do not correlate with expected braking behavior. The sensor may be degraded, producing noisy signals, or stuck at an incor...
The most common cause of C1954 (Master Cylinder Pressure Sensor Circuit Failure) is: Degraded brake pressure sensor transducer producing noisy or drifting output
Typical repair costs for C1954 range from $100 to $550, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Basic braking is unaffected, but brake-assist and stability control brake intervention may not function correctly. The system may over- or under-apply braking force during automatic interventions. Repair soon to maintain full braking system capability.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1954 to identify the root cause.
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Quick Info
Category
Chassis
System
ABS / Brake System
Difficulty
Type
Manufacturer
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