Toyota Sienna Service Manual: 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 fuse and the stop light switch, and the ECM turns the cruise control off.

WIRING DIAGRAM

INSPECTION PROCEDURE

1 READ VALUE OF INTELLIGENT TESTER

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

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)

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

Standard voltage

3 INSPECT STOP LIGHT SWITCH

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

Standard resistance

3. Install the stop light switch.

4 CHECK ECM

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

Standard voltage

REPLACE ECM