Toyota Avalon (XX50) 2019-2022 Service & Repair Manual: Headlight ECU LH Communication Stop Mode

DESCRIPTION

Detection Item

Symptom

Trouble Area

Headlight ECU LH Communication Stop Mode

Any of the following conditions are met:

Communication stop for "HL AutoLeveling/AFS/AHS" is indicated on the "Communication Bus Check" screen of the Techstream.
Click here
Communication stop history for "HL AutoLeveling/AFS/AHS" is indicated on the "Communication Bus Check (Detail)" screen of the Techstream. (The Lost Communication Time value for "HL AutoLeveling/AFS/AHS" is 6 or more.)
Click here
Communication system DTCs (DTCs that start with U) that correspond to "Headlight ECU LH Communication Stop Mode" in "DTC Combination Table" are output.
Click here

WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

NOTICE:

Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.
Click here
Before measuring the resistance of the CAN bus, turn the engine switch off and leave the vehicle for 1 minute or more without operating the key or any switches, or opening or closing the doors. After that, disconnect the cable from the negative (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.
Click here
After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.
DTC check procedure: Turn the engine switch on (IG) and wait for 1 minute or more. Then operate the suspected malfunctioning system and drive the vehicle at 60 km/h (37 mph) or more for 5 minutes or more.
After the repair, perform the CAN bus check and check that all the ECUs and sensors connected to the CAN communication system are displayed as normal.
Click here
Inspect the fuses for circuits related to this system before performing the following procedure.

HINT:

Before disconnecting related connectors for inspection, push in on each connector body to check that the connector is not loose or disconnected.
When a connector is disconnected, check that the terminals and connector body are not cracked, deformed or corroded.

PROCEDURE

1.	CHECK FOR OPEN IN CAN BUS LINES (HEADLIGHT ECU SUB-ASSEMBLY LH BRANCH LINE)

(a) Disconnect the cable from the negative (-) battery terminal.

(b) Disconnect the A8 headlight ECU sub-assembly LH connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
A8-24 (CANH) - A8-23 (CANL)	Cable disconnected from negative (-) battery terminal	54 to 69 Ω

*a	Front view of wire harness connector (to Headlight ECU Sub-assembly LH)

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (HEADLIGHT ECU SUB-ASSEMBLY LH)

2.	CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
A8-12 (GND) - Body ground	Cable disconnected from negative (-) battery terminal	Below 1 Ω

*a	Front view of wire harness connector (to Headlight ECU Sub-assembly LH)

(b) Reconnect the cable to the negative (-) battery terminal.

Standard Voltage:

Tester Connection	Condition	Specified Condition
A8-4 (IG) - Body ground	Engine switch on (IG)	11 to 14 V

REPLACE HEADLIGHT ECU SUB-ASSEMBLY LH

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual > Occupant Classification System(for Hv Model): Front Occupant Classification Sensor LH Collision Detection (B1785)
DESCRIPTION DTC B1785 is stored when the occupant detection ECU receives a collision detection signal sent by the front occupant classification sensor LH in the case of an accident. DTC B1785 is also stored when the front seat assembly RH is subjected to a strong impact, even if an actual accident d ...

Toyota Avalon (XX50) 2019-2022 Owners Manual