DTC    P0571    Stop Light Switch Circuit Malfunction

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DESCRIPTION

While driving with cruise control, if the ECM detects that the brake pedal is depressed, the cruise control system will be canceled. The stop light switch sends brake pedal status signals to the ECM. When the brake pedal is not depressed, terminal ST1- is equal to the positive (+) battery voltage and terminal STP is below 1 V. When the brake pedal is depressed, the ECM cancels cruise control operation. The ECM outputs this DTC 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 Detection Condition
Trouble Area
P0571
ECM detects malfunction of stop light switch circuit under both of following conditions:
  1. Voltage of terminal STP is less than 1 V for 0.5 sec. or more
  2. Voltage of terminal ST- is less than 1 V for 0.5 sec. or more
  1. Stop light switch assembly
  2. Stop light switch circuit
  3. ECM

WIRING DIAGRAM


E110504E02


INSPECTION PROCEDURE

1.READ DATA LIST (STOP LIGHT SWITCH)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch ON, and turn the intelligent tester main switch ON.

  1. Check the DATA LIST for proper functioning of the stop light switch.


ECM (Cruise control): 
Item
Measurement Item / Display (Range)
Normal Condition
Diagnostic Note
Stp Light SW M-CPU
Stop light switch signal (Main CPU) / ON or OFF
ON: Brake pedal is depressed
OFF: Brake pedal is released
-
Stp Light SW S1-CPU
Stop light switch signal (Sub CPU) / ON or OFF
ON: Brake pedal is depressed
OFF: Brake pedal is released
-
Stp Light SW S2-CPU
Stop light switch signal (Sub CPU) / ON or OFF
ON: Brake pedal is depressed
OFF: Brake pedal is released
-

OK:
Display changes according to brake pedal operation described in above table.

HINT:
  1. Stop light SW1 indicates the input of the ST1-terminal, and stop light SW2 indicates the input of the STP terminal.



OK
REPLACE ECM
NG


2.INSPECT FUSE (STOP, IGN)

  1. Remove the STOP and IGN fuses from the instrument panel junction block.

  1. Measure the resistance of the fuses.

    Standard resistance:
    Below 1 Ω



NG
REPLACE STOP LIGHT SWITCH
OK


3.INSPECT STOP LIGHT SWITCH
I013683E06

  1. Disconnect the S14 stop light switch connector.

  1. Measure the resistance of the switch.

    Standard resistance:
    Tester Connection
    		Switch Condition
    		Specified Condition
    1 - 2
    		Not pushed
    		Below 1 Ω
    3 - 4
    		Not pushed
    		10 kΩ or higher
    1 - 2
    		Pushed
    		10 kΩ or higher
    3 - 4
    		Pushed
    		Below 1 Ω



NG
REPLACE STOP LIGHT SWITCH ASSEMBLY
OK


4.CHECK WIRE HARNESS
E110511E03

  1. Measure the voltage of the wire harness side connector.

    Standard voltage:
    Tester Connection
    		Condition
    		Specified Condition
    S14-2 - Body ground
    		Always
    		10 to 14 V
    S14-3 - Body ground
    		Ignition switch ON
    		10 to 14 V



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


5.CHECK ECM (STP, ST1- VOLTAGE)
E110513E01

  1. Reconnect the stop light switch connector.

  1. Disconnect the E14 or E6 connectors from the ECM.

  1. Turn the ignition switch ON.

  1. Measure the voltage of the wire harness side connector.

    Standard voltage:
    1GR-FE:
    Tester Connection
    		Brake Pedal Condition
    		Specified Condition
    E14-15 (STP) - Body ground
    		Depressed
    		10 to 14 V
    E14-15 (STP) - Body ground
    		Released
    		Below 1 V
    E14-16 (ST1-) - Body ground
    		Depressed
    		Below 1 V
    E14-16 (ST1-) - Body ground
    		Released
    		10 to 14 V
    1KD-FTV:
    Tester Connection
    		Brake Pedal Condition
    		Specified Condition
    E6-15 (STP) - Body ground
    		Depressed
    		10 to 14 V
    E6-15 (STP) - Body ground
    		Released
    		Below 1 V
    E6-14 (ST1-) - Body ground
    		Depressed
    		Below 1 V
    E6-14 (ST1-) - Body ground
    		Released
    		10 to 14 V



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

REPLACE ECM