DTC P0571: Stop Light Switch Circuit Malfunction: Procedure

1. Use the Data List to check if the stop light switch is functioning properly. Refer to DATA LIST / ACTIVE TEST .
   RADAR CRUISE
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Stp Light SW M-CPU	Stop light switch (Main CPU) signal / OFF or ON	OFF: Brake pedal released ON: Brake pedal depressed	-

   OK

   On screen, item changes between ON and OFF according to above chart.

NG → See step   4 

OK: Go to next step 

1. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   Vehicle stability control system DTCs are not output.

NG → See step   9 

OK: Go to next step 

1. Clear the DTCs. Refer to DTC CHECK / CLEAR .
2. Perform the following to make sure the DTC detection conditions are met.

   HINT: 

   If the detection conditions are not met, the system cannot detect the malfunction.

   1. Drive the vehicle at a speed of 50 km/h (30 mph) or more.
   2. Turn the cruise control switch on.
   3. Push the cruise control switch to -SET to activate cruise control.
3. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC P0571 is not output.

NG → See step   8 

OK → See step   10 

1. Disconnect the A5 stop light switch connector.
   Fig 1: Identifying A5 Stop Light Switch Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A5-2 - Body ground	Always	11 to 14 V
   A5-4 - Body ground	Engine switch on (IG)	11 to 14 V
   A5-4 - Body ground	Engine switch off	Below 1 V

   TEXT IN ILLUSTRATION
   
   

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

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Remove the stop light switch. Refer to REMOVAL .
   Fig 2: Measuring Stop Light Switch Resistance

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Switch Condition	Specified Condition
   1 - 2	Not pushed	Below 8.3 Ω
   1 - 2	Pushed	10 kΩ or higher
   3 - 4	Pushed	Below 1.6 Ω
   3 - 4	Not pushed	10 kΩ or higher

   TEXT IN ILLUSTRATION
   
   

   *1	Pin
   *a	Not Pushed
   *b	Pushed

NG → See step   7 

OK: Go to next step 

1. Disconnect the A5 stop light switch connector.
2. Disconnect the G44 and G45 ECM connectors.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A5-3 - G44-8 (ST1-)	Always	Below 1 Ω
   A5-1 - G45-18 (STP)	Always	Below 1 Ω
   A5-3 - Body ground	Always	10 kΩ or higher
   A5-1 - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   8