Lexus ES manuals

Lexus ES: Headlight ECU LH Communication Stop Mode

Lexus ES (XZ10) Service Manual / Power Source & Network / Networking / Can Communication System (for Hv Model) / 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.

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  • 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.)

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  • Communication system DTCs (DTCs that start with U) that correspond to "Headlight ECU LH Communication Stop Mode" in "DTC Combination Table" are output.

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  • Headlight ECU sub-assembly LH branch line or connector
  • Power source circuit of headlight ECU sub-assembly LH
  • Headlight ECU sub-assembly LH ground circuit
  • Headlight ECU sub-assembly LH

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.

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  • Before measuring the resistance of the CAN bus, turn the power 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 (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
  • After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.

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  • After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.

    DTC check procedure: Turn the power 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.

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  • 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 (-) auxiliary battery terminal.

(b) Disconnect the A78 headlight ECU sub-assembly LH connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A78-24 (CANH) - A78-23 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

54 to 69 Ω

*a

Front view of wire harness connector

(to Headlight ECU Sub-assembly LH)
NG

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

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

A78-12 (GND) - Body ground

Cable disconnected from negative (-) auxiliary 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 (-) auxiliary battery terminal.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A78-4 (IG) - Body ground

Power switch on (IG)

11 to 14 V
OK

REPLACE HEADLIGHT ECU SUB-ASSEMBLY LH

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

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