Front Fog Light Circuit: Procedure

1. Check the operation of the taillights and headlights.

   OK

   Taillights and headlights operate normally.

NG → See step   8 

OK: Go to next step 

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.
   MAIN BODY
   
   

   Tester Display	Test Part	Control Range	Diagnostic Note
   Front Fog Light Relay	Front fog light relay	ON/OFF	Light control switch is in head position

   OK

   Front fog light relay operates. (Front fog lights come on.)

NG → See step   3 

OK → See step   9 

1. Using a voltmeter, check the signal reading of the engine room junction block assembly. Refer to ON-VEHICLE INSPECTION .

   OK

   Output signal reading is normal.

NG → See step   10 

OK: Go to next step 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Disconnect the 3D instrument panel junction block assembly connector.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   1G-2 - 3D-9	Always	Below 1 Ω
   3D-9 - Body ground	Always	10 kΩ or higher
   1F-13 - 3D-38	Always	Below 1 Ω
   3D-38 - 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.
   Fig 1: Inspecting Instrument Panel Junction Block Assembly Connector Terminals

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   MB-13 (FFGO) - 3D-38	Always	Below 1 Ω
   3D-38 - Body ground	Always	10 kΩ or higher

4. Connect a positive (+) lead from the battery to terminal 3E-1.
5. Connect a negative (-) lead from the battery to terminal MB-14.
6. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   3D-9 - Body ground	Always	11 to 14 V

   TEXT IN ILLUSTRATION
   
   

   *a	Component without harness connected (Instrument Panel Junction Block Assembly)

NG → See step   11 

OK: Go to next step 

1. Replace the engine room junction block assembly with a new or a known good one. Refer to REMOVAL .
2. Check that the fog lights operate normally.

   OK

   The fog lights operate normally.

NG → See step   12 

OK → END (ENGINE ROOM JUNCTION BLOCK ASSEMBLY WAS DEFECTIVE)