What it means
The brake pressure sensor and pedal position sensor disagree by more than the diagnostic tolerance - one indicates pedal action without the other showing pressure, or vice versa.
At a glance
- Usually lights the check-engine light
How it works
The brake pressure sensor measures hydraulic pressure while the brake pedal position sensor reports pedal movement. P05FF sets when their signals do not agree within the system's allowed range, such as pedal movement without the expected pressure change or pressure change without matching pedal input.
Common causes
Most likely first.
- Brake pedal position sensor offset or fault
- Brake pressure sensor offset or fault
- Damaged, loose, or corroded sensor wiring or connectors
- Poor sensor ground or reference voltage
Symptoms
- Check-engine or brake warning light may turn on
- Brake lights may operate inconsistently
- Cruise control may be unavailable
- Brake or stability-control messages may appear
How to diagnose it
- Record freeze-frame data and scan for brake, stability-control, or cruise-control codes that may help identify which signal became implausible.
- With the vehicle safely parked, compare brake pedal position and brake pressure live data while applying and releasing the pedal gently.
- Inspect both sensor connectors and wiring for damage, corrosion, loose pins, or poor grounds, and check relevant fuses and reference supplies.
- Check that each sensor's reading changes smoothly and consistently with pedal application, comparing readings with the manufacturer's specification.
- If wiring and supplies are correct, test the brake pedal position sensor and brake pressure sensor individually before replacing either.
Common fixes
- Secure or clean a loose or corroded connector at either brake sensor.
- Repair damaged wiring, a poor ground, or a faulty reference-supply connection.
- Replace the brake pedal position sensor if its signal is offset or erratic during testing.
- Replace the brake pressure sensor if its output fails the specified pressure correlation test.
Can I keep driving?
Because this code involves brake input signals, do not rely on cruise control and pay close attention to brake warnings, brake lights, and pedal response. If braking feels abnormal or a brake warning remains on, stop safely and have the vehicle inspected before continuing.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.