Headlight Relay Circuit: Procedure

1. Connect Techstream to the DLC3.
2. Turn the ignition switch on (IG).
3. Turn Techstream on.
4. Select the following menu items: Body Electrical / Main Body / Active Test.
5. Check that the relays operate.
   MAIN BODY:
   
   

   Tester Display	Test Part	Control Range	Diagnostic Note
   Headlight Relay	Headlight Relay	ON/OFF	-

   OK

   Headlight relays operate. (Low beam headlights illuminate.)

NG → See step   2 

OK → See step   7 

1. Remove the H-LP LH LO fuse and H-LP RH LO fuse from the engine room junction block assembly.
   Fig 1: Measuring Voltage Of Engine Room Junction Block Assembly (Loading Slots - Body Ground)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the voltage between the loading slot of each fuse and body ground.

   Standard voltage

   Tester Connection	Switch Condition	Specified Condition
   H-LP LH LO fuse terminal - Body ground	Light control switch OFF → HEAD	Below 1 V → 11 to 14 V
   H-LP RH LO fuse terminal - Body ground	Light control switch OFF → HEAD	Below 1 V → 11 to 14 V

NG → See step   3 

OK → REPAIR OR REPLACE HARNESS OR CONNECTOR (FUSE - BODY GROUND) 

1. Remove the engine room junction block assembly from the engine room relay block.
   Fig 2: Measuring Voltage In Engine Room Junction Block Assembly

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the voltage according to the value(s) in the table below.

   Standard voltage

   Tester Connection	Condition	Specified Condition
   2B-4 - Battery negative (-)	Battery positive (+) - 2G-1 Battery negative (-) - 2D-9 Battery negative (-) - 2E-11	11 to 14 V
   2B-5 - Battery negative (-)		11 to 14 V

NG → REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY 

OK: Go to next step 

1. Disconnect the 2G engine room junction block assembly connector.
   Fig 3: Checking Harness And Connector (Battery - Engine Room Junction Block Assembly)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the voltage according to the value(s) in the table below.

   Standard voltage

   Tester Connector	Condition	Specified Condition
   2G-1 - Body ground	Always	11 to 14 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Disconnect the 2D engine room junction block assembly connector.
   Fig 4: Checking Harness And Connector (Engine Room Junction Block Assembly - Main Body ECU)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the 1D instrument panel junction block connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard resistance

   Tester Connection	Condition	Specified Condition
   2D-9 - 1D-3	Always	Below 1 Ω
   2D-9 - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Disconnect the 2E engine room junction block assembly connector.
   Fig 5: Checking Harness And Connector (Engine Room Junction Block Assembly - Body Ground)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance according to the value(s) in the table below.

   Standard resistance

   Tester Connection	Condition	Specified Condition
   2E-11 - Body ground	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → REPLACE MAIN BODY ECU (INSTRUMENT PANEL JUNCTION BLOCK)