P0504 fault code: what it means
P0504: The two brake light switch signals disagree. Cruise control and brake lights may not work properly.
Usual causes, most likely first
- failed brake light switch
- brake pedal switch out of adjustment
- damaged switch wiring
Not sure what P0504 means on your car? Ask Credov.
Before you clear it
Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.
Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.