Dtc P0571 Stop Light Switch Circuit Malfunction

Engine Hybrid System. Yaris. Ncp93, 131
Cruise Control. Yaris. Ncp93, 131

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

INSPECT STOP LIGHT SWITCH OPERATION

INSPECT STOP LIGHT SWITCH ASSEMBLY

INSPECT ECM (STP SIGNAL)

DTC P0571 Stop Light Switch Circuit Malfunction


DESCRIPTION

The cruise control system cancels cruising when the ECM detects that the brake pedal is depressed during cruise control driving. The stop light switch assembly sends signals to the ECM according to the brake pedal conditions. When the brake pedal is released, terminal ST1- is the positive (+) battery voltage, and terminal STP voltage is below 1 V. While the brake pedal is depressed, terminal ST1- is below 1 V, and STP is positive (+) battery voltage. During braking, the ECM cancels cruise control as one of the manual cancel functions.
The ECM outputs this trouble code when the voltage of terminals ST1- and STP are both below 1 V for 0.5 seconds or more at the same time.
The fail-safe function operates to enable normal driving even if there is a malfunction in the stop light signal circuit.

DTC No.
DTC Detected Conditions
Trouble Areas
P0571
ECM detects a malfunction of the stop light switch circuit under both of the following conditions.
  1. Voltage of terminal STP is below 1 V for 0.5 seconds or more.
  2. Voltage of terminal ST1- is below 1 V for 0.5 seconds or more.
  1. Stop light switch assembly
  2. Stop light switch assembly circuit
  3. ECM

WIRING DIAGRAM


Yaris. Ncp93, 131.Cruise Control.Cruise Control System (For Sedan). Dtc P0571 Stop Light Switch Circuit Malfunction


INSPECTION PROCEDURE

1.INSPECT STOP LIGHT SWITCH OPERATION

  1. Check that the stop lights come on while the brake pedal is depressed, and go off when the brake pedal is released.

    OK:
    Brake Pedal Condition
    		Stop Light Condition
    Depressed
    		ON
    Released
    		OFF


NG
INSPECT STOP LIGHT SWITCH CIRCUIT
OK


2.INSPECT STOP LIGHT SWITCH ASSEMBLY


    Yaris. Ncp93, 131.Cruise Control.Cruise Control System (For Sedan). Dtc P0571 Stop Light Switch Circuit Malfunction

  1. Disconnect the stop light switch assembly connector.

  1. Measure the resistance.

    Standard resistance:
    Tester Connection
    		Switch Condition
    		Stop Light Condition
    1 - 2
    		Switch pin free
    (Brake pedal depressed)
    		Below 1Ω
    3 - 4
    		Switch pin free
    (Brake pedal depressed)
    		10 kΩ or higher
    1 - 2
    		Switch pin pushed in
    (Brake pedal released)
    		10 kΩ or higher
    3 - 4
    		Switch pin pushed in
    (Brake pedal released)
    		Below 1Ω

  1. Reconnect the stop light switch assembly connector.



NG
REPLACE STOP LIGHT SWITCH ASSEMBLY (YARIS_NCP93 RM000001DKT021X.html)
OK


3.INSPECT ECM (STP SIGNAL)


    Yaris. Ncp93, 131.Cruise Control.Cruise Control System (For Sedan). Dtc P0571 Stop Light Switch Circuit Malfunction

  1. Disconnect the A21 ECM connector.

  1. Turn the ignition switch to the ON position.

  1. Measure the voltage.

    Standard voltage:
    Tester Connection
    		Brake Pedal Condition
    		Specified Condition
    STP (A21-36) - Body ground
    		Depressed
    		10 to 14 V
    STP (A21-36) - Body ground
    		Released
    		Below 1V
    ST1- (A21-35) - Body ground
    		Depressed
    		Below 1V
    ST1- (A21-35) - Body ground
    		Released
    		10 to 14 V

  1. Reconnect the ECM connector.



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

REPLACE ECM (YARIS_NCP93 RM000001CN002AX.html)