Taillight Relay Circuit [02/2019 - 12/2021]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Body Electrical / Main Body / Active Test.
5. Perform the Active Test according to the display on the Techstream.

   Body Electrical > Main Body > Active Test 

   Tester Display	Measurement Item	Control Range	Diagnostic Note
   Taillight Relay	Taillight relay	OFF or ON	-

   Body Electrical > Main Body > Active Test 

   Tester Display
   Taillight Relay

   OK

   Taillights illuminate.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE 

Refer to PROBLEM SYMPTOMS TABLE [02/2019 - 08/2020] , or refer to PROBLEM SYMPTOMS TABLE [08/2020 - 12/2021]

Result: 

NG 

See step  2

1. Disconnect the instrument panel junction block assembly connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to Instrument Panel Junction Block Assembly)

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

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   4K-1 - Body ground	Power switch off	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  3

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Remove the instrument panel junction block assembly.

   Refer to REMOVAL [02/2019 - 10/2019] , or refer to REMOVAL [10/2019 - 08/2020] , or refer to REMOVAL [08/2020 - 12/2021]

2. Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.

   Refer to REMOVAL [02/2019 - 10/2019] , or refer to REMOVAL [10/2019 - 08/2020] , or refer to REMOVAL [08/2020 - 12/2021]

3. Connect a positive (+) lead from the auxiliary battery to terminal 4K-1.
4. Connect a negative (-) lead from the auxiliary battery to terminal A-14 (TRLY).
5. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   4F-32 - Auxiliary battery negative (-) terminal	Auxiliary battery voltage is applied between terminals 4K-1 - A-14 (TRLY)	11 to 14 V
   4H-30 - Auxiliary battery negative (-) terminal	Auxiliary battery voltage is applied between terminals 4K-1 - A-14 (TRLY)	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) 

Refer to REMOVAL [02/2019 - 10/2019] , or refer to REMOVAL [10/2019 - 08/2020] , or refer to REMOVAL [08/2020 - 12/2021]

Result: 

NG 

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY 

Refer to REMOVAL [02/2019 - 10/2019] , or refer to REMOVAL [10/2019 - 08/2020] , or refer to REMOVAL [08/2020 - 12/2021]