What Does C1953 Mean?
The ABS/stability control module has detected an open circuit in the master cylinder brake pressure sensor. This sensor measures the actual hydraulic pressure being generated by the driver's brake pedal input and is used for brake-assist calibration, ESC brake intervention calculations, and proportional braking logic. Without this sensor, the module cannot accurately gauge how hard the driver is braking. ABS and stability control features may be limited or disabled.
Common Causes
35%
Disconnected or corroded connector at the brake pressure sensor on the master cylinder or ABS unit
25%
Failed brake pressure sensor (internal transducer open circuit)
20%
Broken wire in the harness from the sensor to the ABS module, often from engine bay heat or vibration damage
15%
Corrosion from brake fluid contamination on the sensor or connector (sensor is mounted on the hydraulic unit)
5%
ABS module connector pin damage on the pressure sensor circuit
Diagnostic Steps
1
Locate the master cylinder pressure sensor — it is typically threaded into the ABS hydraulic unit or the master cylinder itself. Verify the electrical connector is fully seated and locked.
2
With the sensor connector disconnected, check for 5V reference voltage and ground from the ABS module. Both must be present; if not, trace the wiring back to the module.
3
Measure continuity on the signal wire, 5V reference, and ground from the sensor connector to the ABS module connector. Engine bay wiring is subject to heat damage and chafing against components.
4
Inspect the sensor for brake fluid weeping at the O-ring seal. Brake fluid is corrosive and will damage electrical connections if it leaks onto the connector. Replace the O-ring and clean the connector if contamination is found.
5
If wiring is intact, reconnect the sensor and monitor the brake pressure PID in live data while gradually pressing the brake pedal. Pressure should rise smoothly from near-zero to the maximum value. No response confirms sensor failure.
Estimated Repair Cost
$80 - $500
Parts + labor, varies by vehicle and location
The ABS/stability control module has detected an open circuit in the master cylinder brake pressure sensor. This sensor measures the actual hydraulic pressure being generated by the driver's brake pedal input and is used for brake-assist calibration, ESC brake intervention calculations, and proporti...
The most common cause of C1953 (Master Cylinder Pressure Sensor Circuit Open) is: Disconnected or corroded connector at the brake pressure sensor on the master cylinder or ABS unit
Typical repair costs for C1953 range from $80 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Basic hydraulic braking still functions normally. However, advanced features like electronic brake-assist, brake force distribution optimization, and ESC brake intervention may be compromised. The vehicle may require more pedal effort in emergency stops without brake-assist. Repair within a reasonable timeframe.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1953 to identify the root cause.
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Quick Info
Category
Chassis
System
ABS / Brake System
Difficulty
Type
Manufacturer
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