Brake System Pressure Sensor Circuit Range/Performance Problem
The brake pressure sensor is reporting incorrect values to the control module.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The brake pressure sensor is not giving valid pressure readings, which may affect braking performance.
What the computer is actually seeing
The brake computer expects to see a voltage ranging from 0.5 to 4.5 volts that corresponds to brake fluid pressure. If the voltage is outside this range or fluctuating wildly, it sets the C1303 code.
What a healthy reading looks like
Brake pressure sensor should read approximately 0.5V at low pressure, increasing up to 4.5V at maximum system pressure, typically around 1800 psi.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check the brake fluid level. It should be at or above the minimum level. If low, top off and retest.
- 22. Inspect the wiring and connectors to the brake pressure sensor for damage or corrosion. Look for loose connections.
- 33. With the key on, engine off, use a multimeter to test the voltage at the brake pressure sensor output. Expected voltage is 0.5 to 4.5V. If it's outside this range, suspect a faulty sensor.
- 44. If the sensor checks out, backprobe the sensor connector and monitor the voltage while actuating the brake pedal. Voltage should change smoothly and correspond with pedal application. If erratic, inspect wiring further.
- 55. If all readings are normal, test the brake master cylinder for internal leaks or failures.
Common causes
- Faulty brake pressure sensor
- Wiring issues or connector faults
- Low brake fluid level
- Faulty brake master cylinder
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to fix this soon, as it can affect brake performance, especially in emergency situations.
Will this code come back after I fix it?
If the underlying issue is resolved, it shouldn't return. Always reset the code and perform a road test to confirm.
Why does it pair with other C1300 series codes?
These codes relate to different aspects of the brake system pressure and function, and can often indicate a common fault.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →