Toyota Venza: Brake Switch "A" / "B" Correlation (P0504)

Toyota Venza Service Manual / 1ar-fe Engine Control / Sfi System / Brake Switch "A" / "B" Correlation (P0504)

DESCRIPTION

The stop light switch is a duplex system that transmits 2 signals: STP and ST1-. These 2 signals are used by the ECM to monitor whether or not the brake system is working properly. If 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.

Signal (ECM Terminal)	Brake Pedal Released	In Transition	Brake Pedal Depressed
STP	OFF	ON	ON
ST1-	ON	ON	OFF

[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.

DTC No.	DTC Detection Condition	Trouble Area
P0504	All of the following conditions continue for 0.5 seconds or more (1 trip detection logic): (a) The ignition switch is ON. (b) The STP signal is OFF when the ST1- signal is OFF.	Short in stop light switch signal circuit Stop light switch assembly ECM

DTC No.

DTC Detection Condition

Trouble Area

P0504

All of the following conditions continue for 0.5 seconds or more (1 trip detection logic):

(a) The ignition switch is ON.

(b) The STP signal is OFF when the ST1- signal is OFF.

Short in stop light switch signal circuit
Stop light switch assembly
ECM

WIRING DIAGRAM

CAUTION / NOTICE / HINT

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 / Data List / Stop Light Switch and ST1.
5. Check the Data List indication when the brake pedal is depressed and released.

Brake Pedal Operation	Stop Light Switch	ST1
Depressed	ON	ON
Released	OFF	OFF

PROCEDURE

1.	INSPECT 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:

Tester Connection	Switch Condition	Specified Condition
A35-2 - Body ground	Always	11 to 14 V
A35-4 - Body ground	Ignition switch ON	11 to 14 V

Text in Illustration

*a	Front view of wire harness connector (to Stop Light Switch Assembly)

REPAIR OR REPLACE HARNESS OR CONNECTOR

2.	INSPECT STOP LIGHT SWITCH ASSEMBLY

(a) Inspect the stop light switch assembly (See page ).

REPLACE STOP LIGHT SWITCH ASSEMBLY

3.	INSPECT ECM (STP AND ST1- VOLTAGE)

(a) Disconnect the ECM connector.

(b) Turn the ignition switch to ON.

Standard Voltage:

Tester Connection	Condition	Specified Condition
A49-39 (ST1-) - Body ground	Brake pedal released	7.5 to 14 V
A49-39 (ST1-) - Body ground	Brake pedal depressed	Below 1.5 V
A49-29 (STP) - Body ground	Brake pedal released	Below 1.5 V
A49-29 (STP) - Body ground	Brake pedal depressed	7.5 to 14 V

Text in Illustration

Brake pedal depressed

Brake pedal released

Front view of wire harness connector

(to ECM)

REPLACE ECM

REPAIR OR REPLACE HARNESS OR CONNECTOR

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