Taillight Relay Circuit [03/2019 - ]: Procedure
WARNING: This page is about a different car, the 2024 Lexus RC F, 2023 Lexus RC F, 2022 Lexus RC F, 2021 Lexus RC F, and 2020 Lexus RC F. However, it is still accessible from the selected car via links, so may be relevant.
- PERFORM ACTIVE TEST USING TECHSTREAM
- Connect the Techstream to the DLC3.
- Turn the engine switch on (IG).
- Turn the Techstream on.
- Enter the following menus: Body Electrical / Main Body / Active Test.
- 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
Taillight relay operates. (Taillights illuminate.)
Result
Proceed to OK NG
Result:
OK
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to PROBLEM SYMPTOMS TABLE [03/2019 - 01/2023] , or refer to PROBLEM SYMPTOMS TABLE [01/2023 - ]
Result:
NG
See step 2
- CHECK HARNESS AND CONNECTOR (BATTERY - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)
- Disconnect the 4E instrument panel junction block assembly connector.
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Connection Condition Specified Condition 4E-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
- INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY
*a Component without harness connected
(Instrument Panel Junction Block Assembly)- - - Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.
Refer to REMOVAL [09/2014 - ]
- Connect a positive (+) lead from the battery to terminal 4E-1.
- Connect a negative (-) lead from the battery to terminal MB-14 (TRLY).
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Connection Condition Specified Condition 4C-5 - Battery negative (-) terminal Always 11 to 14 V 4D-28 - 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 [09/2014 - ]
Result:
NG
REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY. Refer to REMOVAL [09/2014 - ]
- Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.