DTC C1A05: Stop Light Switch Circuit [11/2017 - 01/2023]: Procedure

1. Disconnect the A52 stop light switch assembly connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A52-1 (B) - Body ground	Always	11 to 14 V
   A52-5 (B) - Body ground	Engine switch on (IG)	11 to 14 V

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A52-3 (GND) - Body ground	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  2

1. Inspect the stop light switch assembly.

   Refer to ON-VEHICLE INSPECTION [09/2014 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  COMPONENTS [09/2014 - ] 

Result: 

OK 

See step  3

1. Disconnect the Q2 driving support ECU assembly connector.
2. Disconnect the A52 stop light switch assembly connector.
3. Disconnect the A13 certification ECU (smart key ECU assembly) connector.
4. Disconnect the A86 brake actuator assembly (skid control ECU) connector.
5. Disconnect the O45 transmission floor shift assembly (shift lock control unit) connector.
6. Disconnect the 2D stop light relay (semiconductor power integration ECU) connector.
7. Disconnect the A77 ECM connector.
8. Disconnect the A79 TCM connector.
9. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Q2-15 (STP-) - A52-2 (L)	Always	Below 1 Ω
   Q2-1 (ST1-) - A52-4 (L)	Always	Below 1 Ω
   Q2-15 (STP-) or A52-2 (L) - Body ground	Always	10 kΩ or higher
   Q2-1 (ST1-) or A52-4 (L) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE DRIVING SUPPORT ECU ASSEMBLY. Refer to  COMPONENTS [09/2014 - 01/2023] 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR