Taillight Relay Circuit [10/2018 - 07/2022]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
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 [10/2018 - 10/2019]  Refer to  PROBLEM SYMPTOMS TABLE [10/2019 - 10/2020]  Refer to  PROBLEM SYMPTOMS TABLE [10/2020 - 07/2022] 

Result: 

NG 

See step  2

1. Disconnect the 4F instrument panel junction block assembly connector.
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   FOR HV MODEL
   
   

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

   FOR GASOLINE MODEL
   
   

   Tester Connection	Condition	Specified Condition
   4F-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

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

   Refer to REMOVAL [10/2018 - 07/2022]

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

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a

   Component without harness connected (Instrument Panel Junction Block Assembly)

   -

   -

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   4D-30 - Auxiliary 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 [10/2018 - 07/2022] 

Result: 

NG 

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY. Refer to  REMOVAL [10/2018 - 07/2022]