Headlight Relay Circuit [08/2017 - 08/2019]: Procedure

1. Using the Techstream, perform the Active Test.

   Refer to DATA LIST / ACTIVE TEST [08/2017 - 08/2019]

   MAIN BODY
   
   

   Tester Display	Test Part	Control Range	Diagnostic Note
   Headlight	Headlight relay (H-LP LO)	OFF or ON	-

   OK

   Headlight relay (H-LP LO) operates (low beam headlights turn on).

   Result

   Proceed to
   OK
   NG

Result: 

OK 

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [08/2017 - 08/2019] 

Result: 

NG 

See step  2

1. Remove the headlight relay (H-LP LO) from the engine room relay block and junction block.
2. Inspect the headlight relay (H-LP LO).

   Refer to ON-VEHICLE INSPECTION [08/2017 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE HEADLIGHT RELAY (H-LP LO) 

Result: 

OK 

See step  3

1. Remove the headlight relay (H-LP LO) from the engine room relay block and junction block.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to Headlight Relay [H-LP LO])

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   Headlight relay terminal (H-LP LO) 1 - Body ground	Always	11 to 14 V
   Headlight relay (H-LP LO) terminal 3 - Body ground	Always	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  4

1. Remove the headlight relay (H-LP LO) from the engine room relay block and junction block.
2. Disconnect the 3H cowl side junction block LH connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Headlight relay (H-LP LO) terminal 2 - 3H-31	Always	Below 1 Ω
   Headlight relay (H-LO) terminal 2 or 3H-31 - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  5

1. Remove the cowl side junction block LH.

   Refer to REMOVAL [08/2017 - 08/2019]

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Component without harness connected (Cowl Side Junction Block LH)

2. Remove the main body ECU (multiplex network body ECU) from the cowl side junction block LH.

   Refer to REMOVAL [08/2017 - 08/2019]

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   3H-31 - A-15 (HRLY)	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [08/2017 - 08/2019] 

Result: 

NG 

REPLACE COWL SIDE JUNCTION BLOCK LH. Refer to  REMOVAL [08/2017 - 08/2019]