Toyota Venza: Brake Switch "A" Circuit (P0571)

Toyota Venza Service Manual / Cruise Control / Cruise Control System / Brake Switch "A" Circuit (P0571)

DESCRIPTION

When the brake pedal is depressed, the stop light switch assembly sends a signal to the ECM. When the ECM receives this signal, it cancels the cruise control. The fail-safe function operates to enable normal driving even if there is a malfunction in the stop light signal circuit. Cruise control cancellation occurs when voltage is applied to terminal STP. When the brake is applied, voltage is normally applied to terminal STP of the ECM through the STOP fuse and the stop light switch assembly, and the ECM turns the cruise control off.

DTC	DTC Detection Condition	Trouble Area
P0571	Voltage of STP signal and that of ST1- signal of ECM are less than 1 V for 0.5 seconds or more	Stop light switch assembly Stop light switch circuit ECM

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

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

PROCEDURE

1.	INSPECT STOP LIGHT SWITCH ASSEMBLY (POWER SOURCE)

(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	Condition	Specified Condition
A35-2 - Body ground	Always	11 to 14 V

Text in Illustration

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

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

2.	INSPECT STOP LIGHT SWITCH ASSEMBLY (POWER SOURCE)

(a) Disconnect the stop light switch assembly connector.

(b) Turn the ignition switch to ON.

Standard Voltage:

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

Text in Illustration

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

(d) Reconnect the stop light switch assembly connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - IGN FUSE)

3.	INSPECT STOP LIGHT SWITCH ASSEMBLY

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

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

Standard Resistance:

Tester Connection	Switch Condition	Specified Condition
1 - 2	Switch pin not pushed	Below 1 Ω
3 - 4	Switch pin not pushed	10 kΩ or higher
1 - 2	Switch pin pushed	10 kΩ or higher
3 - 4	Switch pin pushed	Below 1 Ω

REPLACE STOP LIGHT SWITCH ASSEMBLY

4.	CHECK HARNESS AND CONNECTOR (ECM - STOP LIGHT SWITCH ASSEMBLY)

(a) Disconnect the ECM connector.

(b) Disconnect the stop light switch assembly connector.

Standard Resistance (Check for Open):

For 1AR-FE

Tester Connection	Condition	Specified Condition
A49-29 (STP) - A35-1	Always	Below 1 Ω
A49-39 (ST1-) - A35-3	Always	Below 1 Ω

For 2GR-FE

Tester Connection	Condition	Specified Condition
A41-36 (STP) - A35-1	Always	Below 1 Ω
A41-35 (ST1-) - A35-3	Always	Below 1 Ω

Standard Resistance (Check for Short):

For 1AR-FE

Tester Connection	Condition	Specified Condition
A49-29 (STP) or A35-1 - Body ground	Always	10 kΩ or higher
A49-39 (ST1-) or A35-3 - Body ground	Always	10 kΩ or higher

For 2GR-FE

Tester Connection	Condition	Specified Condition
A41-36 (STP) or A35-1 - Body ground	Always	10 kΩ or higher
A41-35 (ST1-) or A35-3 - Body ground	Always	10 kΩ or higher

Text in Illustration

*1	Front view of wire harness connector (to Stop Light Switch Assembly)
*2	Front view of wire harness connector (to ECM)
*3	for 1AR-FE
*4	for 2GR-FE

(d) Reconnect the stop light switch assembly connector.

(e) Reconnect the ECM connector.

Result	Proceed to
NG	A
OK (for 1AR-FE)	B
OK (for 2GR-FE)	C

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

REPLACE ECM

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