P0504

1NZ-FE 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 a Techstream.









WIRING DIAGRAM





INSPECTION PROCEDURE
HINT:
- Read freeze frame data using a Techstream. 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.
- STP signal conditions can be checked using the Techstream.
1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the tester ON.
4. Select the following menu items: Powertrain / Engine and ECT / All Data / Stop Light Switch.
5. Check the STP signal when the brake pedal is depressed and released.





PROCEDURE

1. CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL B VOLTAGE)




(a) Disconnect the A13 stop light switch connector.
(b) Turn the ignition switch to ON.
(c) Measure the voltage between the terminals of the A13 stop light switch connector and body ground.
Standard voltage:





(d) Reconnect the stop light switch connector.
NG -- INSPECT FUSE (STOP AND IGN FUSE)
OK -- Continue to next step.
2. INSPECT STOP LIGHT SWITCH ASSEMBLY




(a) Remove the stop light switch assembly.
(b) Check the resistance.
Standard resistance:





(c) Reinstall the stop light switch assembly.
NG -- REPLACE STOP LIGHT SWITCH ASSEMBLY
OK -- Continue to next step.
3. INSPECT ECM (STP AND ST1 - VOLTAGE)




(a) Disconnect the A21 ECM connector.
(b) Turn the ignition switch to ON.
(c) Measure the voltage between the terminals ST1- and STP of the A21 ECM connector and body ground.
Standard voltage:





(d) Reconnect the ECM connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM
4. INSPECT FUSE (STOP AND IGN FUSE)




(a) Remove the STOP and IGN fuses from the main body ECU.
(b) Check the resistance.
Standard resistance:
Below 1 Ohms
(c) Reinstall the STOP and IGN fuses.
NG -- CHECK FOR SHORTS IN ALL HARNESSES AND CONNECTORS CONNECTED TO FUSE AND REPLACE FUSE
OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR