Share a caseSign in
ElectricalSeverity Medium: diagnose soon

P0504Brake Switch "A"/"B" Correlation

What it means

The two brake switch signals (one normally open, one normally closed) don't agree.

Symptoms

  • Cruise control not working
  • Brake light problems
  • Possibly reduced engine power (brake/throttle plausibility)

Common causes

  • Faulty or misadjusted brake light switch
  • Wiring fault
  • Blown fuse

What to check first

  1. Watch both brake switch signals in live data while pressing the pedal
  2. Adjust or replace the switch
  3. Check fuses and wiring
Can I drive with P0504? Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

Cases with P0504 (0)

Share yours

No published cases with this code yet.

Colleagues asking about P0504

Ask for help

Stuck on P0504? Describe what you measured and ask the community.

P0504: questions and answers

What does P0504 mean?

P0504: Brake Switch "A"/"B" Correlation. The two brake switch signals (one normally open, one normally closed) don't agree.

What are the symptoms of P0504?

Cruise control not working. Brake light problems. Possibly reduced engine power (brake/throttle plausibility).

What causes P0504?

Faulty or misadjusted brake light switch. Wiring fault. Blown fuse.

How do you diagnose P0504?

1. Watch both brake switch signals in live data while pressing the pedal 2. Adjust or replace the switch 3. Check fuses and wiring

Can I drive with P0504?

Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.