DTC C1A05: Stop Light Switch Circuit: Procedure

1. Depress the brake pedal and check that the stop lights illuminate.

   OK

   The stop lights illuminate when the brake pedal is depressed and turn off when the brake pedal is released.

NG → See step   8 

OK: Go to next step 

1. Disconnect the A77 stop light switch assembly connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

2. Disconnect the A33 driving support ECU connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A77-2 (L) - A33-11 (STP-)	Always	Below 1 Ω
   A77-4 (L) - A33-34 (ST1-)	Always	Below 1 Ω
   A77-2 (L) - Body ground	Always	10 kΩ or higher
   A77-4 (L) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Disconnect the A33 driving support ECU connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A5-2 (L) - Body ground	Brake pedal released	Below 1 V
   A77-4 (L) - Body ground	Brake pedal released	Below 1 V
   A77-2 (L) - Body ground	Brake pedal pushed	11 to 14 V
   A77-4 (L) - Body ground	Brake pedal pushed	11 to 14 V

NG → See step   9 

OK: Go to next step 

1. Clear the DTCs. Refer to DTC CHECK / CLEAR [09/2012 - ] .
2. Make sure the following conditions are met:

   HINT: 

   If the detection conditions are not met, the system cannot detect malfunctions.

   • Radar cruise control system:

     The vehicle is being driven at a speed of approximately 50 km/h (31 mph) or more and the ACC main switch is on.

   • Lane keeping assist system:

     The vehicle is being driven at a speed of approximately 50 km/h (31 mph) or more and the lane-keeping assist main switch is on.

   • The brake pedal is depressed for 1 second or more.
3. Check for DTCs. Refer to DTC CHECK / CLEAR [09/2012 - ] .

   OK

   DTC P0504 is not output.

NG → See step   7 

OK: Go to next step 

1. Check for DTCs. Refer to DTC CHECK / CLEAR [09/2012 - ] .

   OK

   DTC C1A05 is not output.

   NOTE:

   When replacing the driving support ECU, always replace it with a new one and be sure to perform initialization. Refer to INITIALIZATION [09/2012 - ] . If an ECU which was installed to another vehicle is used, the information stored in the ECU will not match the information from the vehicle, and as a result, a DTC may be stored.

NG → See step   6 

OK → END (STOP LIGHT SWITCH ASSEMBLY IS DEFECTIVE)