P0504

DTC P0504 BRAKE SWITCH "A"/"B" CORRELATION

CIRCUIT DESCRIPTION

DTC Detection Conditions:

The stop lamp switch is a duplex system that transmits two signals: STP and ST1-. These two signals are used by the ECM to monitor whether or not the brake system is working properly. If the signals, which indicate the brake pedal is being depressed and released, are detected simultaneously, the ECM interprets this as a malfunction in the stop lamp switch and sets the DTC.

HINT: The normal conditions are as shown in the table. The signals can be read using a hand-held tester.

Wiring Diagram:

INSPECTION PROCEDURE

HINT: Read freeze frame data using a hand-held tester or OBD II scan tool. Freeze frame data record the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data, from the time the malfunction occurred.

Step 1 - 2:

Step 3:

Step 4:

Hand-held tester

Step 1 - 3:

Step 3 (Contd.) - 4:

OBD II scan tool (excluding the hand-held tester)

CHECK FOR INTERMITTENT PROBLEMS

HINT: Hand-held tester only:
Inspect the vehicle's ECM using check mode. Intermittent problems are easier to detect with a hand-held tester when the ECM is in check mode. In check mode, the ECM uses 1trip detection logic, which is more sensitive to malfunctions than normal mode (default), which uses 2trip detection logic.

a. Clear DTCs.
b. Switch the ECM from normal mode to check mode using a hand-held tester.
c. Perform a simulation test.
d. Check and wiggle the harness(es), connector(s) and terminal(s).