Taillight Relay Circuit [06/2018 - ]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the engine 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 [06/2018 - 08/2020]  , or refer to  PROBLEM SYMPTOMS TABLE [08/2020 - 08/2021]  , or refer to  PROBLEM SYMPTOMS TABLE [08/2021 - ] 

Result: 

NG 

See step  2

1. Disconnect the 3K instrument panel junction block assembly connector.
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   3K-1 - Body ground	Always	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 main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.

   Refer to REMOVAL [06/2018 - 08/2021] , or refer to REMOVAL [08/2021 - 09/2022] , or refer to REMOVAL [09/2022 - ]

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   3H-30 - Battery negative (-) terminal	Always	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [06/2018 - 08/2021]  , or refer to  REMOVAL [08/2021 - 09/2022]  , or refer to  REMOVAL [09/2022 - ] 

Result: 

NG 

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY. Refer to  REMOVAL [06/2018 - 08/2021]  , or refer to  REMOVAL [08/2021 - 09/2022]  , or refer to  REMOVAL [09/2022 - ]