Toyota Sienna Service Manual: Brake Switch "A" Circuit

Toyota Sienna Service Manual / Cruise control / Dynamic laser cruise control system / Diagnostic trouble code chart / Brake Switch "A" Circuit

DTC P0571 Brake Switch "A" Circuit

DESCRIPTION

When the brake pedal is depressed, the stop light switch 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. The cancellation condition 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 SW fuse and the stop light switch, and the ECM turns the cruise control off.

DTC No.	DTC Detection Condition	Trouble Area
P0571	Voltage of STP terminal and that of ST1- terminal of ECM are less than 1 V for 0.5 sec. or more	Stop light switch Stop light switch circuit ECM

WIRING DIAGRAM

WIRING DIAGRAM

INSPECTION PROCEDURE

1 READ VALUE OF INTELLIGENT TESTER

Connect the intelligent tester to the DLC3.
Turn the ignition switch to the ON position, and turn the intelligent tester main switch on.
Check the DATA LIST for proper functioning of the stop light switch.

ECM (Cruise control):

ECM (Cruise control)

OK: When the brake pedal is operated, the display changes as shown above.

REPLACE ECM

2 CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - BATTERY)

CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - BATTERY)

Disconnect the S12 stop light switch connector.
Measure the voltage according to the value(s) in the table below.

Standard voltage

Standard voltage

3 INSPECT STOP LIGHT SWITCH

INSPECT STOP LIGHT SWITCH

Remove the stop light switch.
Measure the resistance according to the value(s) in the table below.

Standard resistance

Standard resistance

4 CHECK ECM

CHECK ECM

Reconnect the S12 stop light switch connector.
Disconnect the E4 connector from the ECM.
Turn the ignition switch to the ON position.
Measure the voltage according to the value(s) in the table below.

Standard voltage

Standard voltage

REPLACE ECM

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