Headlight Relay Circuit: 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 the operation.
   MAIN BODY
   
   

   Tester Display	Test Part	Control Range	Diagnostic Note
   Headlight Relay	LO-beam headlight relay	ON/OFF	-

   OK

   Headlight relays operate (LO-beam headlights illuminate).

NG → See step   2 

OK → See step   6 

1. Disconnect the 2D engine room junction block assembly connector.
   Fig 1: 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
   2D-1 - Body ground	Always	11 to 14 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Disconnect the 2A and 2B engine room junction block assembly connectors.
   Fig 2: 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
   2A-17 - Body ground	Always	Below 1 Ω
   2B-8 - Body ground	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

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

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

   Standard resistance

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

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Remove the engine room junction block assembly from the engine room relay block.
   Fig 4: Measuring Voltage Of Engine Room Junction Block Assembly

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Connect a positive (+) lead from the battery to terminal 2D-1.
3. Connect a negative (-) lead from the battery to terminals 2A-3, 2A-17 and 2B-8.
4. Measure the voltage according to the value(s) in the table below.

   Standard voltage

   Tester Connection	Condition	Specified Condition
   2B-3 - Battery negative	Always	11 to 14 V
   2B-4 - Battery negative	Always	11 to 14 V

NG → REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY 

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