Toyota Avalon (XX50) 2019-2022 Service & Repair Manual: Taillight Relay Circuit

DESCRIPTION

The main body ECU (multiplex network body ECU) controls the operation of the TAIL relay.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.
Before replacing the main body ECU (multiplex network body ECU), refer to Registration.
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PROCEDURE

1.	PERFORM ACTIVE TEST USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(d) Enter the following menus: Body Electrical / Main Body / Active Test.

(e) 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.

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

2.	CHECK HARNESS AND CONNECTOR (POWER SOURCE - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

(a) Disconnect the 4K instrument panel junction block assembly connector.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
4K-1 - Body ground	Always	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.	INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

Component without harness connected

(Instrument Panel Junction Block Assembly)

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

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(b) Connect a positive (+) lead from the battery to terminal 4K-1.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
4H-30 - Battery negative (-) terminal	Always	11 to 14 V

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual > Telematics System(for Gasoline Model): Problem Symptoms Table
PROBLEM SYMPTOMS TABLE HINT: Use the table below to help determine the cause of problem symptoms. If multiple suspected areas are listed, the potential causes of the symptoms are listed in order of probability in the "Suspected Area" column of the table. Check each symptom by checking the suspected ...

Toyota Avalon (XX50) 2019-2022 Owners Manual