DTC P0571: Stop Light Switch Circuit Malfunction: Procedure

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

   Result

   Condition	Illumination Condition
   Brake pedal depressed	ON
   Brake pedal released	OFF

   OK

   When the brake pedal is operated, the illumination changes as shown above.

NG → See step   7 

OK: Go to next step 

1. Turn the engine switch off.
2. Remove the BRK-LP relay from the engine room No. 3 relay block.
   Fig 1: Identifying BRK-LP Relay

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   3 - 5	Voltage is not applied between terminals 1 and 2	10 kΩ or higher
   3 - 5	Voltage is applied between terminals 1 and 2	Below 1 Ω
   3 - 4	Voltage is not applied between terminals 1 and 2	Below 1 Ω
   3 - 4	Voltage is applied between terminals 1 and 2	10 kΩ or higher

NG → REPLACE BRK-LP RELAY 

OK: Go to next step 

1. Measure the voltage according to the value(s) in the table below.
   Fig 2: Identifying BRK-LP Relay

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   BRK-LP relay terminal 5 - Body ground	Always	11 to 14 V
   BRK-LP relay terminal 2 - Body ground	Engine switch on (IG)	11 to 14 V
   BRK-LP relay terminal 2 - Body ground	Engine switch off	Below 1 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Disconnect the connector from the brake actuator (skid control ECU).
   Fig 3: Identifying Engine Room No. 3 Relay Block And SKID Control ECU Connector A62

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A62-31 (STPO) - BRK-LP relay terminal 1	Always	Below 1 Ω
   A62-31 (STPO) - Body ground	Always	10 kΩ or higher

3. Disconnect the connector from the brake actuator (skid control ECU).

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Disconnect the connector from the stop light control relay.
   Fig 4: A62 Connector End View

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A62-2 (STP1) - J96-2 (STP)	Always	Below 1 Ω
   A62-2 (STP1) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   6