Low Beam Headlight Circuit: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Body Electrical / Main Body / Active Test.
5. According to the display on the Techstream, perform the Active Test.
   MAIN BODY
   
   

   Techstream Display	Test Part	Control Range	Diagnostic Note
   Headlight Relay	Headlight relay	OFF or ON	-

   OK

   Headlight relay (H-LP relay) operates (Low beam headlights illuminate).

NG → See step   2 

OK → See step   7 

1. Inspect the headlight relay (H-LP relay). Refer to ON-VEHICLE INSPECTION .

NG → REPLACE HEADLIGHT RELAY (H-LP RELAY) 

OK: Go to next step 

1. Remove the headlight relay (H-LP relay) from the No. 2 motor compartment relay block.
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   Relay Terminal 1 - Body ground	Power switch off	11 to 14 V
   Relay Terminal 5 - Body ground	Power switch off	11 to 14 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Remove the headlight relay (H-LP relay) from the No. 2 motor compartment relay block.
2. Disconnect the A58 headlight assembly LH connector.
3. Disconnect the A59 headlight assembly RH connector.
4. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Relay Terminal 3 - A58-1 (LO)	Always	Below 1 Ω
   Relay Terminal 3 - A59-1 (LO)	Always	Below 1 Ω
   Relay Terminal 3 - Body ground	Always	10 kΩ or higher
   A58-2 (E) - Body ground	Always	Below 1 Ω
   A59-2 (E) - Body ground	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Remove the headlight relay (H-LP relay) from the No. 2 motor compartment relay block.
2. Disconnect the 3B 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
   Relay terminal 2 - 3B-34	Always	Below 1 Ω
   Relay terminal 2 - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Remove the instrument panel junction block assembly. Refer to REMOVAL .
2. Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly. Refer to REMOVAL .
3. Measure the resistance according to the value(s) in the table below.
   Fig 1: Measuring Resistance Of Instrument Panel Junction Block Assembly Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   TEXT IN ILLUSTRATION
   
   

   *a

   Component without harness connected (Instrument Panel Junction Block Assembly)

   -

   -

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   3B-34 - MB-15 (HRLY)	Always	Below 1 Ω

NG → See step   8 

OK → See step   9