Inspection Procedure

1. Turn the dimmer switch ON and check that the headlights illuminate.

   OK: Headlights illuminate. 

OK: REPLACE MULTIPLEX NETWORK FRONT LIGHT ECU 

Fig 1: Identifying Multiplex Network Front Light ECU Connectors Terminal

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG: Go to next step. 

1. Remove the MPX-B3 fuse from the passenger side junction block.
2. Measure the resistance of the fuse.

   Standard resistance: Below 1 Ω 

NG: REPLACE FUSE 

OK: Go to next step. 

1. Measure the voltage and resistance of the wire harness side connectors.
   NOTE: The inspection should be performed from the backside of the relay block with the multiplex network front light ECU connector connected.

   Standard voltage 

   VOLTAGE SPECIFICATION
   
   

   Tester Connection	Specified Condition
   Relay block front light ECU terminal 8 (FMB3) - Body ground	10 to 14 V

   Standard resistance 

   RESISTANCE SPECIFICATION
   
   

   Tester Connection	Specified Condition
   Relay block front light ECU terminal 12 (GND) - Body ground	Below 1 Ω

NG: REPAIR OR REPLACE HARNESS AND CONNECTOR 

OK: Go to next step. 

1. Remove the front light ECU from the engine room No. 2 relay block.
2. Disconnect the A31 and G3 ECU connectors.
   Fig 2: Identifying Front Light ECU And A31 And G3 ECU Connectors

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. Measure the resistance of the wire harness side connectors.

   Standard resistance 

   RESISTANCE SPECIFICATION
   
   

   Tester Connection	Specified Condition
   Relay block front light ECU terminal 5 (MPX1) - G3-17 (MPL2)	Below 1 Ω
   Relay block front light ECU terminal 6 (MPX2) - A31-5 (MPX1)	Below 1 Ω

   Result 

   RESULT CHART
   
   

   Result	Proceed to
   Both are OK	A
   One is OK	B
   Both are NG	C

B: REPLACE MULTIPLEX NETWORK FRONT LIGHT ECU AND REPAIR OR REPLACE HARNESS AND CONNECTOR 

C: REPAIR OR REPLACE HARNESS AND CONNECTOR 

A: REPLACE MULTIPLEX NETWORK FRONT LIGHT ECU