Dtc P0504 Brake Switch A / B Correlation

Engine. Lexus Gs430, Gs300. Uzs190 Grs190
3Gr-Fe Engine Control System. Lexus Gs430, Gs300. Uzs190 Grs190

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK OPERATION OF STOP LIGHT

READ VALUE OF INTELLIGENT TESTER (STP SIGNAL AND ST1 - VOLTAGE)

INSPECT STOP LIGHT SWITCH ASSEMBLY

CHECK ECM (STP, ST1 - VOLTAGE)

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 an intelligent tester.

Signal
Brake Pedal Released
In Transition
Brake Pedal Depressed
STP
OFF
ON
ON
ST1-
ON
ON
OFF

DTC No.
DTC Detection Condition
Trouble Area
P0504
Conditions (a), (b) and (c) continue for 0.5 seconds or more
(1 trip detection logic):
(a) Engine switch on (IG)
(b) Brake pedal released
(c) STP signal OFF when ST1- signal OFF
  1. Short in stop light switch signal circuit
  2. Stop light switch
  3. ECM

WIRING DIAGRAM


Lexus Gs430, Gs300. Uzs190 Grs190.3Gr-Fe Engine Control System.Sfi System. Dtc P0504 Brake Switch A / B Correlation


INSPECTION PROCEDURE

HINT:
Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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.
1.CHECK OPERATION OF STOP LIGHT

  1. 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 CIRCUIT
OK


2.READ VALUE OF INTELLIGENT TESTER (STP SIGNAL AND ST1 - VOLTAGE)
Lexus Gs430, Gs300. Uzs190 Grs190.3Gr-Fe Engine Control System.Sfi System. Dtc P0504 Brake Switch A / B Correlation

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG) and turn the tester ON.

  1. Enter the following menus: Powertrain / Engine / Data List / Stop Light Switch.

  1. Check the STP signal when the brake pedal is depressed and released.

    OK:
    Brake Pedal Operation
    		Specified Condition
    Depressed
    		STP signal ON
    Released
    		STP signal OFF

  1. Measure the voltage between the terminals of the A6 and E7 ECM connectors.

    Standard voltage:
    Tester Connection
    		Brake Pedal Operation
    		Specified Condition
    ST1- (A6-8) - E1 (E7-7)
    		Depressed
    		Below 1.5 V
    ST1- (A6-8) - E1 (E7-7)
    		Released
    		7.5 to 14 V


OK
CHECK FOR INTERMITTENT PROBLEMS
NG


3.INSPECT STOP LIGHT SWITCH ASSEMBLY
Lexus Gs430, Gs300. Uzs190 Grs190.3Gr-Fe Engine Control System.Sfi System. Dtc P0504 Brake Switch A / B Correlation

  1. Remove the stop light switch assembly.

  1. Measure the resistance.

    Standard resistance:
    Switch Position
    		Tester Connection
    		Specified Condition
    Switch pin free
    		1 - 2
    		Below 1 Ω
    Switch pin free
    		3 - 4
    		10 kΩ or higher
    Switch pin pushed in
    		1 - 2
    		10 kΩ or higher
    Switch pin pushed in
    		3 - 4
    		Below 1 Ω

  1. Reinstall the stop light switch assembly.



NG
REPLACE STOP LIGHT SWITCH ASSEMBLY
OK


4.CHECK ECM (STP, ST1 - VOLTAGE)
Lexus Gs430, Gs300. Uzs190 Grs190.3Gr-Fe Engine Control System.Sfi System. Dtc P0504 Brake Switch A / B Correlation

  1. Disconnect the A6 and A7 ECM connectors.

  1. Measure the voltage of the ECM connector. Measure the voltage between the terminals of the A6 and A7 ECM connectors.

    Standard voltage:
    Tester Connection
    		Brake Pedal Operation
    		Specified Condition
    STP (A7-4) - Body ground
    		Depressed
    		9 to 14 V
    STP (A7-4) - Body ground
    		Released
    		0 to 3 V
    ST1- (A6-8) - Body ground
    		Depressed
    		0 to 3 V
    ST1- (A6-8) - Body ground
    		Released
    		9 to 14 V


NG
REPAIR OR REPLACE HARNESS AND CONNECTOR
OK

REPLACE ECM