P0504

1NR-FE ENGINE CONTROL: SFI SYSTEM: P0504: Brake Switch "A" / "B" Correlation
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 stores the DTC.

HINT
The normal signal conditions are as shown in the table below.





- [OFF] denotes ground potential.
- [ON] denotes battery potential (+B).
- On the Techstream, both the Data List items Stop Light Switch and ST1 are ON when the brake pedal is depressed because the ST1 indication characteristic is opposite to the Stop Light Switch indication.





WIRING DIAGRAM





INSPECTION PROCEDURE

NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.

HINT
- Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. 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.
- Stop light switch conditions can be checked using the Techstream.
(1) Connect the Techstream to the DLC3.
(2) Turn the ignition switch to ON.
(3) Turn the Techstream on.
(4) Enter the following menus: Powertrain / Engine and ECT / Data List / Stop Light Switch and ST1.
(5) Check the Data List indication when the brake pedal is depressed and released.






PROCEDURE

1. INSPECT STOP LIGHT SWITCH ASSEMBLY (POWER SOURCE VOLTAGE)

(a) Disconnect the stop light switch connector assembly.





(b) Turn the ignition switch to ON.

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:





Text in Illustration





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BATTERY)
OK -- Continue to next step.

2. INSPECT STOP LIGHT SWITCH ASSEMBLY

(a) Remove the stop light assembly switch.





(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:





Text in Illustration





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

3. INSPECT ECM (STP AND ST1 - VOLTAGE)

(a) Disconnect the ECM connector.





Text in Illustration





(b) Turn the ignition switch to ON.

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ECM)

OK -- REPLACE ECM Removal