DTC C1A4B: Stop Light Relay Circuit [08/2014 - ]: Procedure

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

   OK

   Condition	Illumination Condition
   Brake pedal depressed	On
   Brake pedal released	Off

NG → See step   13 

OK: Go to next step 

1. Turn the power switch off.
2. Disconnect the A28 stop light control relay connector.
3. Measure the voltage according to the value(s) in the table below.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A28-6 (+B) - Body ground	Always	11 to 14 V

   TEXT IN ILLUSTRATION
   
   

   *1	Front view of wire harness connector (to Stop Light Control Relay)

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Turn the power switch off.
2. Disconnect the A28 stop light control relay connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A28-8 (GND) - Body ground	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Turn the power switch off.
2. Disconnect the A58 brake booster with master cylinder (skid control ECU) connector.
3. Measure the voltage according to the value(s) in the table below.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A58-33 (STP) - Body ground	Brake pedal depressed	11 to 14 V
   A58-33 (STP) - Body ground	Brake pedal released	Below 1.5 V

   TEXT IN ILLUSTRATION
   
   

   *1	Front view of wire harness connector (to Brake Booster with Master Cylinder (Skid Control ECU))

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Turn the power switch off.
2. Disconnect the A28 stop light control relay connector.
3. Measure the voltage according to the value(s) in the table below.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A28-5 (STP) - Body ground	Brake pedal depressed	11 to 14 V
   A28-5 (STP) - Body ground	Brake pedal released	Below 1.5 V

   TEXT IN ILLUSTRATION
   
   

   *1	Front view of wire harness connector (to Stop Light Control Relay)

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Enter the following menus: Chassis / ABS/VSC/TRAC / Active Test.
2. Perform "Active Test" according to the display on Techstream.

   Tester Display	Measurement Item	Control Range	Diagnostic Note
   Stop Light Relay	Stop light control relay (STOP LP)	ON or OFF	Stop lights come on

3. Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Stop Light Relay Output	Stop light control relay (STOP LP) output/ ON or OFF	ON: Relay output on (Stop light on) OFF: Relay output off (Stop light off)	-

   Result

   Result	Result
   Data List item changes between ON and OFF, but stop lights do not turn on	A
   Data List item changes between ON and OFF and stop lights turn on and off	B

B → See step   8 

A: Go to next step 

1. Turn the power switch off.
2. Disconnect the A58 brake booster with master cylinder (skid control ECU) connector.
3. Disconnect the A28 stop light control relay connector.
4. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A58-3 (STPO) - A28-9 (ACC)	Always	Below 1 Ω
   A58-3 (STPO) - A28-9 (ACC)	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Turn the power switch off.
2. Disconnect the A58 brake booster with master cylinder (skid control ECU) connector.
3. Disconnect the A28 stop light control relay connector.
4. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A58-6 (STP2) - A28-1 (OUT)	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Turn the power switch off.
2. Disconnect the A58 brake booster with master cylinder (skid control ECU) connector.
3. Measure the voltage according to the value(s) in the table below.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A58-6 (STP2) - Body ground	Brake pedal depressed	11 to 14 V
   A58-6 (STP2) - Body ground	Brake pedal released	Below 1.5 V

   TEXT IN ILLUSTRATION
   
   

   *1	Front view of wire harness connector (to Brake Booster with Master Cylinder (Skid Control ECU))

NG → See step   12 

OK: Go to next step 

1. Turn the power switch off and wait for at least 2 minutes.
2. Clear the DTCs. Refer to DTC CHECK / CLEAR [08/2014 - ] .
3. Make sure that the DTC detection conditions are met.

   HINT: 

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

   • Using the Techstream, perform the Active Test "Stop Light Relay" with the power switch on (IG).
4. Check for DTCs. Refer to DTC CHECK / CLEAR [08/2014 - ] .

   Result

   Result	Result
   DTC C1A4B is not output	A
   DTC C1A4B is output	B

   NOTE:

   When replacing the driving support ECU, always replace it with a new one. If a driving support ECU which was installed to another vehicle is used, the information stored in the driving support ECU will not match the information from the vehicle. As a result, a DTC may be stored.

B → See step   11 

A → END