Headlight ECU LH Communication Stop Mode [10/2019 - ]: Procedure

1. Disconnect the cable from the negative (-) auxiliary battery terminal.
2. Disconnect the A78 headlight ECU sub-assembly LH connector.
3. Measure the resistance according to the value(s) in the table below.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A78-24 (CANH) - A78-23 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

   Result

   Result
   OK
   NG

Result: 

NG 

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

Result: 

OK 

See step  2

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

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A78-12 (GND) - Body ground	Cable disconnected from negative (-) auxiliary battery terminal	Below 1 Ω

2. Reconnect the cable to the negative (-) auxiliary battery terminal.
3. 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

   Result

   Result
   OK
   NG

Result: 

OK 

REPLACE HEADLIGHT ECU SUB-ASSEMBLY LH. Refer to  REMOVAL [06/2018 - 09/2022]  , or refer to  REMOVAL [09/2022 - ] 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)