Low Beam Headlight Circuit [08/2020 - ]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Enter the following menus: Body Electrical / Main Body / Active Test.
5. Check that the relay operates.

   Body Electrical > Main Body > Active Test 

   Tester Display	Measurement Item	Control Range	Diagnostic Note
   Headlight Relay	Low beam headlights	ON or OFF	-

   Body Electrical > Main Body > Active Test 

   Tester Display
   Headlight Relay

   OK

   Headlight relay operates. (Low beam headlights illuminate.)

   Result

   Proceed to
   OK
   NG

Result: 

OK 

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [08/2020 - 12/2021]  , or refer to  PROBLEM SYMPTOMS TABLE [12/2021 - ] 

Result: 

NG 

See step  2

1. Remove the No. 1 integration relay from the No. 1 engine room relay block.

   Refer to REMOVAL [08/2020 - ]

2. Inspect the No. 1 integration relay.

   Refer to INSPECTION [02/2017 - ]

   OK

   No. 1 integration relay is normal.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE NO. 1 INTEGRATION RELAY. Refer to  REMOVAL [08/2020 - ] 

Result: 

OK 

See step  3

1. Measure the voltage according to the value(s) in the chart below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   1A-5 - Body ground	Always	11 to 14 V
   1B-8 - Body ground	Always	11 to 14 V

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Rear view of wire harness connectors (to No. 1 integration relay)
   *b	H-LP LH Relay terminal
   *c	H-LP RH Relay terminal

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  4

1. Disconnect the A87 headlight assembly LH connector.
2. Disconnect the A89 headlight assembly RH connector.
3. Measure the resistance according to the value(s) in the chart below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   1B-1 - A87-7 (LO)	Always	Below 1 Ω
   1A-12 - A89-7 (LO)	Always	Below 1 Ω
   A87-1 (E) - Body ground	Always	Below 1 Ω
   A89-1 (E) - Body ground	Always	Below 1 Ω
   1B-1 - Body ground	Always	10 kΩ or higher
   1A-12 - 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. Disconnect the 3F instrument panel junction block assembly connector.
2. Measure the resistance according to the value(s) in the chart below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   1A-11 - 3F-31	Always	Below 1 Ω
   1B-2 - 3F-31	Always	Below 1 Ω
   1A-11 or 3F-31 - Body ground	Always	10 kΩ or higher
   1B-2 or 3F-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  6

1. Remove the instrument panel junction block assembly.

   Refer to REMOVAL [08/2020 - 12/2021] , or refer to REMOVAL [12/2021 - ]

2. Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.
3. Measure the resistance according to the value(s) in the chart below.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a

   Component without harness connected (Instrument Panel Junction Block Assembly)

   -

   -

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   3F-31 - MB-15 (HRLY)	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [08/2020 - 12/2021]  , or refer to  REMOVAL [12/2021 - ] 

Result: 

NG 

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY. Refer to  REMOVAL [08/2020 - 12/2021]  , or refer to  REMOVAL [12/2021 - ]