P0504

1ZZ-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 Techstream.









WIRING DIAGRAM





INSPECTION PROCEDURE

HINT: Read freeze frame data using 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 be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

PROCEDURE

1. CHECK STOP LIGHT (OPERATION)
(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) Check the resistance.
Standard resistance:





(c) Reinstall the stop light switch assembly.
NG -- REPLACE STOP LIGHT SWITCH ASSEMBLY
OK -- Continue to next step.
3. READ VALUE OF TECHSTREAM (STP SIGNAL AND ST1 - VOLTAGE)





(a) Connect Techstream to the DLC3.
(b) Turn the ignition switch to the ON position and turn the tester on.
(c) Select the following menu items: Powertrain / Engine and ECT / Data List / Stop Light Switch.
(d) Check the STP signal when the brake pedal is depressed and released.
Standard:





(e) Measure the voltage between the terminals of the E3 and E5 ECM connectors.
Standard voltage:





OK -- CHECK FOR INTERMITTENT PROBLEMS
NG -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - ECM)





(a) Disconnect the S7 stop light switch connector.
(b) Disconnect the E5 ECM connector.
(c) Check the resistance.
Standard resistance (Check for open):





(d) Reconnect the stop light switch connector.
(e) Reconnect the ECM connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM