P0504
PowertrainBrake Switch A/B Correlation
The engine control unit has detected conflicting signals from the two brake pedal position switch circuits, indicating they are not correlating correctly.
ⓘ Information only. This page provides general educational information about fault code P0504. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0504 mean?
P0504 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Brake Switch A/B Correlation.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
About ABS / ESP codes
Codes in this category relate to the anti-lock braking system (ABS) and electronic stability control (ESP/ESC). These systems share wheel speed sensors, hydraulic modulators, and a common control module. Faults here usually disable ABS pulse braking and stability control assistance, but standard hydraulic brakes continue working normally.
P0504 is one of 429 codes in this category. Browse all ABS / ESP codes →
What we know about P0504 specifically
We record the SAE J2012 standardised definition and the system this code belongs to, but we have not yet published detailed driver-reported symptoms, common causes, or step-by-step diagnostic guidance for P0504.
Rather than invent that information by generating generic content from a template, we leave it out. For specific guidance, the most reliable sources are:
- •your vehicle's own service manual or manufacturer-specific technical bulletins
- •a qualified mechanic with a manufacturer-level diagnostic tool
- •a marque specialist familiar with your make and model
Codes nearby
Codes adjacent to P0504 in the P-code series. Many fault codes appear together with their neighbours because they relate to the same circuit or component.
Other ABS / ESP codes
Other fault codes in the same system as P0504. The ones with detailed guides have plain-English explanations, symptoms, causes, and diagnostic steps.
Spotted an issue or have something to add? Mechanics, technicians, and drivers who have first-hand experience with P0504 can submit a correction or expansion. We review every submission before publishing, mechanic submissions are prioritised.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →