P0504 : Brake Switch "A"/"B" Correlation

P0504 means the two internal circuits of the brake light switch do not agree. Modern brake switches send two signals to the ECU for safety: one that closes when the pedal is pressed and one that opens. If the ECU sees both circuits in the same state at the same time, it sets P0504. The fix is almost always a new brake switch, sometimes combined with a pedal position adjustment.

P0504 est un code defaut lie a electrique, classe en gravite moderate. Lorsque le calculateur de ton vehicule detecte cette condition, il enregistre P0504 et allume le voyant moteur.

Si ton vehicule a declenche P0504, tu peux remarquer un ou plusieurs de ces symptomes :

• Cruise control will not engage or drops out as soon as it is set
• Brake lights stay on continuously or do not come on at all
• Push-button start refuses to crank the engine
• Automatic transmission will not shift out of Park
• Stability control or hill-hold features disabled

Voici les causes les plus courantes de P0504, classees selon la probabilite qu'elles soient en cause :

Non, regle ca immediatement. Most modern brake pedal switches have two redundant circuits. When they disagree, the ECU cannot trust the brake pedal input. Cruise control will not work, brake lights may stay on or fail, and on push-button start vehicles the engine may refuse to start. Repair before extended driving.

Suis ces etapes pour identifier la cause profonde de P0504 :

1. Use a scan tool to view live brake switch data. Most ECUs show two signals (BLS and BTS or similar). Press the pedal and verify both change state cleanly together
2. Inspect the pedal at rest. The switch plunger should be fully extended and resting against the pedal stop with no preload. A loose stop pad lets the pedal sit too low and pre-presses the switch
3. Remove the connector and inspect for bent pins or corrosion. Reseat firmly and recheck
4. If both signals stay correlated only when the connector is wiggled, repair the wiring. Otherwise, replace the brake switch as a unit
5. Clear codes, perform any required relearn for cruise control, and confirm the brake lights work both at rest and when the pedal is pressed

Les couts de reparation de P0504 varient selon la cause profonde et ton vehicule. Voici des estimations courantes :

P0504 se comporte differemment selon ton vehicule. Selectionne ta voiture ci-dessous pour des causes propres au modele, les problemes connus et des estimations de couts ajustees :

Ces codes apparaissent souvent avec P0504 ou indiquent des problemes connexes :