How to Solve the P0504 Trouble Code?
2 Answers
P0504 trouble code can be resolved by replacing the brake switch. The causes of the P0504 trouble code include: water-induced short circuit in the brake switch; poor connection of the brake switch; damaged brake switch; related circuit faults; control unit faults. More information about the P0504 trouble code is as follows: 1. The P0504 trouble code refers to the correlation of Brake Switch A/B, expressed in English as: Brake Switch A/B Correlation. 2. The function of the brake switch: It transmits braking information in the form of electrical signals to the ECU to control the vehicle's speed, serving as an important basis for stopping cruise control and disengaging the torque converter. 3. The brake switch has two contact switches: normally open contact switch; normally closed contact switch. The brake switch controls the brake lights and ABS system, providing signals to the engine braking system.
I still remember clearly when I encountered the P0504 trouble code last time—I was on the highway when the cruise control suddenly stopped working, which gave me quite a scare. After getting home, I pulled out the OBD scanner to read the code and confirm the issue. The first step was to check the brake lights, and sure enough, they didn’t light up when I pressed the pedal, indicating a problem with the brake switch. I crawled under the driver’s seat, found that small switch, and discovered that a loose screw had caused it to shift out of position. After tightening and adjusting it, I cleared the fault code and restarted the car—everything was back to normal. Actually, this P0504 code indicates a brake signal inconsistency, commonly caused by switch failure or loose wiring. A simple check is to see if the lights turn on. Ignoring it can affect ABS and braking safety, potentially leading to a rear-end collision. My advice is to fix the problem as soon as possible, starting with the easiest solutions and not delaying.
