DTC C1A05: Stop Light Switch Circuit [10/2017 - 09/2020]: Procedure

1. Disconnect the A56 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
   A56-1 (B) - Body ground	Always	11 to 14 V
   A56-5 (B) - Body ground	Engine switch on (IG)	11 to 14 V

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A56-3 (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. Disconnect the M2 driving support ECU assembly connector.
2. Disconnect the A56 stop light switch assembly connector.
3. Disconnect the A13 certification ECU (smart key ECU assembly) connector.
4. Disconnect the A105 brake actuator assembly (skid control ECU) connector.
5. Disconnect the K46 transmission floor shift assembly (shift lock control unit) connector.
6. Disconnect the 2D stop light relay (semiconductor power integration ECU) connector.
7. For 2GR-FKS:
   1. Disconnect the A106 ECM connector.
8. For 8AR-FTS:
   1. Disconnect the A91 ECM connector.
9. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   M2-15 (STP-) - A56-2 (L)	Always	Below 1 Ω
   M2-1 (ST1-) - A56-4 (L)	Always	Below 1 Ω
   M2-15 (STP-) or A56-2 (L) - Body ground	Always	10 kΩ or higher
   M2-1 (ST1-) or A56-4 (L) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  3

1. Replace the stop light switch assembly.

   Refer to REMOVAL [04/2013 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  4

1. Clear the DTCs.

   Refer to DTC CHECK / CLEAR [10/2016 - 09/2020]

   Powertrain > Radar Cruise > Clear DTCs 

2. Check for DTCs.

   Refer to DTC CHECK / CLEAR [10/2016 - 09/2020]

   Powertrain > Radar Cruise > Trouble Codes 

   Result

   Result	Proceed to
   DTC C1A05 is not output	A
   DTC C1A05 is output	B

Result: 

A 

END (STOP LIGHT SWITCH ASSEMBLY WAS DEFECTIVE) 

Result: 

B 

REPLACE DRIVING SUPPORT ECU ASSEMBLY. Refer to  COMPONENTS [04/2013 - 09/2020]