P0504

1UR-FSE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0504: Brake Switch "A" / "B" Correlation

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

DESCRIPTION

The stop light 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 light switch and sets the DTC.
HINT: The normal conditions are as shown in the table below. The signals can be read using the Techstream.









WIRING DIAGRAM





INSPECTION PROCEDURE
HINT: Read freeze frame data using the Techstream. Freeze frame data records 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.

PROCEDURE

1. CHECK OPERATION OF STOP LIGHT
(a) Check whether the stop lights turn on and off normally when the brake pedal is depressed and released.
OK:
Stop lights turn ON when brake pedal is depressed.
NG -- REPAIR OR REPLACE STOP LIGHT SWITCH CIRCUIT
OK -- Continue to next step.

2. INSPECT STOP LIGHT SWITCH ASSEMBLY




(a) Remove the stop light switch assembly.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:






NG -- REPLACE STOP LIGHT SWITCH ASSEMBLY
OK -- Continue to next step.

3. READ VALUE USING TECHSTREAM (STP SIGNAL AND ST1- VOLTAGE)




(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream ON.
(c) Enter the following menus: Powertrain / Engine / Data List / All Data / Stop Light Switch.
(d) Check the STP signal when the brake pedal is depressed and released.
Standard:





(e) Measure the voltage according to the value(s) in the table below.
Standard Voltage:






OK -- CHECK FOR INTERMITTENT PROBLEMS
NG -- Continue to next step.

4. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - ECM)




(a) Disconnect the A35 stop light switch connector.
(b) Disconnect the A14 ECM connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance (Check for open):






Standard Resistance (Check for short):






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM