DTC P0703-12: Brake Switch "B" Circuit Short to Battery [12/2019 - 10/2022]: Procedure

1. According to the display on the GTS, read the Data List while the vehicle is being driven.

   Powertrain > Transmission > Data List 

   Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
   Stop Light SW	Stop light switch status	ON or OFF	ON: Brake pedal depressed OFF: Brake pedal released	-

   Powertrain > Transmission > Data List 

   Tester Display
   Stop Light SW

   Result

   Result	Proceed to
   Data List value is normal	A
   Data List value is not normal	B

Result: 

A 

SYMPTOMS SIMULATION AND DTC CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2019 - ] 

Result: 

B 

See step  2

1. Check the stop light switch assembly installation condition.

   Refer to INSTALLATION [12/2019 - ]

   OK

   Stop light switch assembly is installed correctly.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REINSTALL STOP LIGHT SWITCH ASSEMBLY CORRECTLY. Refer to  INSTALLATION [12/2019 - ] 

Result: 

OK 

See step  3

1. Inspect the stop light switch assembly.

   Refer to ON-VEHICLE INSPECTION [12/2019 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  COMPONENTS [12/2019 - ] 

Result: 

OK 

See step  4

1. Disconnect the A28 ECM connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Brake pedal depressed	*b	Brake Pedal Released
   *c	Front view of wire harness connector (to ECM)	-	-

2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A28-27 (STP) - Body ground	Brake pedal released	Below 1.5 V
   	Brake pedal depressed	7.5 to 14 V

   HINT: 

   If there is a short in the STP terminal circuit, there may be a malfunction in the circuit of a connected ECU.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

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

Result: 

OK 

See step  5

1. Replace the ECM.

   Refer to COMPONENTS [12/2019 - 10/2022]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

PERFORM REGISTRATION. Refer to  REGISTRATION [12/2019 - 10/2022]