Transmission Control Systems

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

CIRCUIT DESCRIPTION

The purpose of this circuit is to prevent the engine from stalling while driving in lock-up condition, when brakes are suddenly applied. When the brake pedal is depressed, this switch sends a signals to the ECM.

Then the ECM cancels the operation of the lock-up clutch while braking is in progress.

Wiring Diagram:

Step 1:

Step 2 - 3:

INSPECTION PROCEDURE

HINT: Read freeze frame data using hand-held tester or OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.