DTC P0571: Stop Light Switch Circuit Malfunction: Procedure

1. Check the Data List for proper functioning of the stop light switch.
   CRUISE CONTROL
   
   

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

   OK

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

OK → REPLACE ECM 

NG: Go to next step 

Fig 1: Inspecting Stop Light Switch Assembly

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the stop light switch connector.
2. Measure the resistance of the switch.

   Standard voltage

   Tester Connection	Switch Condition	Specified Condition
   1 - 2	Pin not pushed (Brake pedal depressed)	Below 1 Ω
   3 - 4	Pin not pushed (Brake pedal depressed)	10 kΩ or higher
   1 - 2	Pin pushed (Brake pedal released)	10 kΩ or higher
   3 - 4	Pin pushed (Brake pedal released)	Below 1 Ω

NG → REPLACE STOP LIGHT SWITCH 

OK: Go to next step 

Fig 2: Checking Wire Harness (ECM - Body Ground)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the E5 and E6 ECM connectors.
2. Turn the ignition switch ON.
3. Measure the voltage of the wire harness side connectors.

   Standard voltage

   Tester Connection	Brake Pedal Condition	Specified Condition
   E5-4 (STP) - Body ground	Depressed	10 to 14 V
   E5-4 (STP) - Body ground	Released	Below 1 V
   E6-8 (ST1-) - Body ground	Depressed	Below 1 V
   E6-8 (ST1-) - Body ground	Released	10 to 14 V

   RESULT
   
   

   Result	Proceed to
   OK	A
   NG (STP terminal is NG)	B
   NG (ST1- terminal is NG)	C

C → REPAIR OR REPLACE HARNESS OR CONNECTOR 

A → REPLACE ECM 

B: Go to next step 

1. Remove the STOP fuse from the driver side junction block ECU.
2. Measure the resistance of the fuse.

   Standard resistance

   Below 1 Ω

NG → REPLACE FUSE 

OK: Go to next step 

1. Disconnect the D2 ECU connector.
2. Measure the voltage of the wire harness side connector.
   Fig 3: Checking Wire Harness (Main Body ECU -- Battery)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard voltage

   Tester Connection	Brake Pedal Condition	Specified Condition
   D2-13 (STPI) - Body ground	Depressed	10 to 14 V
   D2-13 (STPI) - Body ground	Released	Below 1 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Reconnect the D2 ECU connector.
2. Measure the voltage according to the value(s) in the table below.
   Fig 4: Identifying D2 Driver Side Junction Block Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard voltage

   Tester Connection	Brake Pedal Condition	Specified Condition
   D2-12 (STPO) - Body ground	Depressed	10 to 14 V
   D2-12 (STPO) - Body ground	Released	Below 1 V

NG → REPLACE MAIN BODY ECU (for Driver Side) 

OK → REPAIR OR REPLACE HARNESS OR CONNECTOR (MAIN BODY ECU - ECM)