Headlight Dimmer Switch 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 / Data List.
5. Read the display on the Techstream.
   MAIN BODY
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Dimmer Hi SW	Dimmer switch high position signal/ON or OFF	ON: Dimmer switch in high or high flash (pass) position OFF: Dimmer switch in low position	-
   Passing Light SW	Dimmer switch high flash (pass) position signal/ON or OFF	ON: Dimmer switch in high flash (pass) position OFF: Dimmer switch not in high flash (pass) position	-
   Front Fog Light SW	Front fog light switch signal/ON or OFF	ON: Front fog light switch on OFF: Front fog light switch off	-
   Light Auto SW	Light control switch AUTO position signal/ON or OFF	ON: Light control switch in AUTO position OFF: Light control switch not in AUTO position	-
   Headlight SW	Light control switch head position signal/ON or OFF	ON: Light control switch in head position OFF: Light control switch not in head position	-
   Taillight SW	Light control switch tail position signal/ON or OFF	ON: Light control switch in tail or head position OFF: Light control switch in neither tail nor head position	-

   OK

   Normal conditions listed above are displayed.

NG → See step   2 

OK → See step   4 

HINT: 

Inspect the items that did not change as a result of monitoring the Data List.

1. Remove the headlight dimmer switch assembly. Refer to REMOVAL .
   Fig 1: Checking Headlight Dimmer Switch Assembly

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

   Standard Resistance

   LIGHT CONTROL SWITCH
   
   

   Tester Connection	Switch Condition	Specified Condition
   12 (EL) - 18 (T)	Light control switch off	10 kΩ or higher
   18 (T) - 19 (A)	Light control switch off	10 kΩ or higher
   19 (A) - 20 (H)	Light control switch off	10 kΩ or higher
   12 (EL) - 18 (T)	Light control switch in tail position	Below 1 Ω
   12 (EL) - 18 (T)	Light control switch in head position	Below 1 Ω
   18 (T) - 20 (H)	Light control switch in head position	Below 1 Ω
   12 (EL) - 19 (A)	Light control switch in AUTO position	Below 1 Ω

   DIMMER SWITCH
   
   

   Tester Connection	Switch Condition	Specified Condition
   11 (HU) - 12 (EL)	Dimmer switch in low position	10 kΩ or higher
   11 (HU) - 12 (EL)	Dimmer switch in high position	Below 1 Ω
   12 (EL) - 17 (HF)	Dimmer switch in high flash position	Below 1 Ω

   FRONT FOG LIGHT SWITCH
   
   

   Tester Connection	Switch Condition	Specified Condition
   3 (LFG) - 4 (BFG)	Fog light switch off	10 kΩ or higher
   3 (LFG) - 4 (BFG)	Fog light switch on	Below 1 Ω

   OK

   Headlight dimmer switch assembly is normal.

   TEXT IN ILLUSTRATION
   
   

   *a	Component without harness connected (Headlight Dimmer Switch Assembly)

NG → See step   5 

OK: Go to next step 

1. Disconnect the L47 headlight dimmer switch assembly connector.
2. Disconnect the L7 main body ECU (multiplex network body ECU) connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   L47-4 (BFG) - L7-27 (FFOG)	Always	Below 1 Ω
   L47-11 (HU) - L7-5 (HU)	Always	Below 1 Ω
   L47-17 (HF) - L7-8 (HF)	Always	Below 1 Ω
   L47-18 (T) - L7-30 (TAIL)	Always	Below 1 Ω
   L47-19 (A) - L7-28 (A)	Always	Below 1 Ω
   L47-20 (H) - L7-29 (HEAD)	Always	Below 1 Ω
   L47-4 (BFG) - Body ground	Always	10 kΩ or higher
   L47-11 (HU) - Body ground	Always	10 kΩ or higher
   L47-17 (HF) - Body ground	Always	10 kΩ or higher
   L47-18 (T) - Body ground	Always	10 kΩ or higher
   L47-19 (A) - Body ground	Always	10 kΩ or higher
   L47-20 (H) - Body ground	Always	10 kΩ or higher
   L47-12 (EL) - Body ground	Always	Below 1 Ω
   L47-3 (LFG) - Body ground	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   6