Battery, charging and glow plugs

P0504 Brake pedal switch: readings don't match ("A")

By: Diagno editorial team · Updated: 2026-10-15

P0504 means: Brake pedal switch: readings don't match ("A"). The brake pedal switch tells the computer when the brake is pressed. Drive gently and have the car checked soon. The most common repair costs about €50–100 in Estonia, depending on make and model. The most common cause: brake light switch faulty or out of adjustment.

Is it safe to drive?Get it checked soonDrive gently and have the car checked soon.

Switch replacement€50–100parts and labour in Estonia, depending on make and model

What it means

The brake pedal switch tells the computer when the brake is pressed. A wrong signal can affect the brake lights, cruise control and the gear selector lock.

What you may notice

Brake lights don't work or stay on
Cruise control doesn't work
Automatic selector won't come out of P

What could be wrong

1Brake light switch faulty or out of adjustment · Switch replacement €50–100
2Wire or connector · Wiring or connector repair €45–90
3Brake light bulb or fuse · Fuse replacement and cause check €30–60

Repair difficulty: Easy

What you can check yourself

Have someone check that the brake lights come on when you press the pedal. Don't drive without brake lights. You can do the simpler checks yourself.

How we fix it

We check the switch signals on the diagnostic tool
We adjust or replace the switch
We repair the wiring

Standard SAE description: Brake Switch "A"/"B" Correlation

Check the fuse · If a light, the horn, wipers, a socket or the fuel pump is dead, a blown fuse may be the cause.Fuse boxes by car →

Want a definite answer?

Bring the car to our workshop in Estonia for diagnostics. We read the fault codes, test the sensors and tell you what is wrong. Repair price depends on the work involved, generally €45 per hour.

Book a diagnostic check

Questions

What does fault code P0504 mean?

Brake pedal switch: readings don't match ("A"). The brake pedal switch tells the computer when the brake is pressed. A wrong signal can affect the brake lights, cruise control and the gear selector lock.

Can I drive with code P0504?

Drive gently and have the car checked soon.

How much does it cost to fix P0504?

It depends on the cause: switch replacement €50–100; wiring or connector repair €45–90; fuse replacement and cause check €30–60. Prices include labour at €45/h, depending on make and model.

How is P0504 fixed?

We check the switch signals on the diagnostic tool. We adjust or replace the switch. We repair the wiring.

Based on AI combined with our hands-on workshop experience and knowledge. This information is general and prices are approximate (Estonian workshop rates). The same code can mean different things on different cars. Only an inspection of the car gives a definite answer.