P0504

2GR-FE ENGINE CONTROL: SFI SYSTEM: P0504: Brake Switch "A" / "B" Correlation
P0504 - Brake Switch "A" / "B" Correlation

DESCRIPTION

The stop light switch assembly 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 assembly 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 signal conditions can be checked using the Techstream.
(1) Connect the Techstream to the DLC3.
(2) Turn the engine switch on (IG).
(3) Turn the Techstream on.
(4) Enter the following menus: Powertrain / Engine / Data List / Stop Light Switch and ST1.
(5) Check the Data List indication when the brake pedal is depressed and released.






PROCEDURE

1. CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL VOLTAGE)

(a) Disconnect the stop light switch assembly connector.





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

Standard Voltage:





Text in Illustration





(c) Reconnect the stop light switch assembly connector.

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

2. CHECK STOP LIGHT SWITCH ASSEMBLY (TERMINAL VOLTAGE)

(a) Disconnect the stop light switch assembly connector.





(b) Turn the engine switch on (IG).

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

Standard Voltage:





Text in Illustration





(d) Reconnect the stop light switch assembly connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - IG2 RELAY)
OK -- Continue to next step.

3. INSPECT STOP LIGHT SWITCH ASSEMBLY

(a) Inspect the stop light switch assembly Testing and Inspection.

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

4. CHECK ECM (STP AND ST1- VOLTAGE)

(a) Disconnect the ECM connector.





(b) Turn the engine switch on (IG).

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

Standard Voltage:





Text in Illustration





(d) Reconnect the ECM connector.

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

OK -- REPLACE ECM Removal