LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2008 >> LS 460L >> Repair and Diagnosis >> Body & Frame >> Windows >> Windshield/WINDOWGLASS >> Window Defogger System >> Rear Window Defogger System Does Not Operate >> Inspection Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Inspection Procedure

  1. CHECK OPERATION (ENGINE START) 
    1. Check that the engine starts normally.

      OK: Engine starts normally. 

    NG: GO TO SMART ACCESS SYSTEM WITH PUSH-BUTTON START  (See HOW TO PROCEED WITH TROUBLESHOOTING )

    OK: Go to next step 

  2. PERFORM ACTIVE TEST BY TECHSTREAM (DEFOGGER RELAY) 
    1. Select the Active Test, using the Techstream to generate a control command, and then check that the rear window defogger operates.

      Air Conditioner 

      ACTIVE TEST TABLE

      Tester Display Test Part Control Range Diagnostic Note
      Defogger Relay (Rear) Rear window defogger relay operation OFF/ON -

      Result 

      RESULT TABLE

      Result Proceed to
      Rear window defogger operates normally (w/ Multi-display) A
      Rear window defogger operates normally (w/o Multi-display) B
      Rear window defogger does not operate C

    B: Go to step   4 

    C: Go to step   5 

    A: Go to next step 

  3. CHECK MULTI-DISPLAY (OPERATION) 
    1. Temporarily replace the multi-display with a new or normally functioning one (see REMOVAL ).
    2. Check that the malfunction disappears.

      OK: Malfunction disappears. 

    NG: REPLACE AIR CONDITIONING AMPLIFIER  (See REMOVAL )

    OK: REPLACE MULTI-DISPLAY  (See REMOVAL )

  4. CHECK INTEGRATION CONTROL AND PANEL (OPERATION) 
    1. Temporarily replace the integration control and panel with a new or normally functioning one (see REMOVAL ).
    2. Check that the malfunction disappears.

      OK: Malfunction disappears. 

    NG: REPLACE AIR CONDITIONING AMPLIFIER  (See REMOVAL )

    OK: REPLACE INTEGRATION CONTROL AND PANEL  (See REMOVAL )

  5. INSPECT FUSE (DEFOG, D-IG1-3) 
    1. Remove the DEFOG H-fuse from the engine room No. 1 relay block.
    2. Remove the D-IG1-3 fuse from the main body ECU.
    3. Measure the resistance of the fuses.

      Standard resistance 

      RESISTANCE SPECIFICATION TABLE

      Tester Connection Condition Specified Condition
      DEFOG H-fuse Always Below 1 Ω
      D-IG1-3 fuse Always Below 1 Ω

    NG: REPLACE FUSE 

    OK: Go to next step 

  6. INSPECT DEFOGGER RELAY (DEFOG) 
    1. Remove the defogger relay from the relay block No. 3.
    2. Measure the resistance according to the value(s) in the table below.

      Standard resistance 

      RESISTANCE SPECIFICATION TABLE

      Tester Connection Condition Specified Condition
      3 - 4 When battery voltage is not applied between terminals Below 1 Ω
      3 - 5 When battery voltage is not applied between terminals 10 kΩ or higher
      3 - 4 When battery voltage is applied to terminals 1 and 2 10 kΩ or higher
      3 - 5 When battery voltage Is applied to terminals 1 and 2 Below 1 Ω
      Fig 1: Identifying Defogger Relay (Marking - DEFOG)
      G04952245Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPLACE DEFOGGER RELAY 

    OK: Go to next step 

  7. CHECK HARNESS AND CONNECTOR (DEFOGGER RELAY - FRONT LIGHT ECU AND BATTERY) 
    1. Remove the defogger relay from the No. 3 relay block.
    2. Disconnect the A51 front light ECU connector.
    3. Measure the voltage according to the value(s) in the table below.

      Standard voltage 

      VOLTAGE SPECIFICATION TABLE

      Tester Connection Switch Condition Specified Condition
      Defogger relay terminal 2 - Body ground Engine switch on (IG) 11 to 14 V
      Defogger relay terminal 5 - Body ground Always 11 to 14 V
    4. Measure the resistance according to the value(s) in the table below.

      Standard resistance 

      RESISTANCE SPECIFICATION TABLE

      Tester Connection Condition Specified Condition
      Defogger relay terminal 1 - A51-12 (RDEF) Always Below 1 Ω
      Fig 2: Identifying A51 Front Light ECU Connector
      G04952246Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  8. CHECK HARNESS AND CONNECTOR (REAR WINDOW DEFOGGER - DEFOGGER RELAY AND BODY GROUND) 
    1. Disconnect the S19 and W1 defogger connectors.
    2. Disconnect the defogger relay from the No. 3 relay block.
    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance 

      RESISTANCE SPECIFICATION TABLE

      Tester Connection Condition Specified Condition
      S19-1 - Defogger relay terminal 3 Always Below 1 Ω
      W1 -1 - Body ground Always Below 1 Ω
      Defogger relay terminal 4 - Body ground Always Below 1 Ω
      S19-1 - Body ground Always 10 kΩ or higher
      Fig 3: Identifying S19 & W1 Defogger Connectors
      G04952247Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  9. INSPECT REAR WINDOW DEFOGGER WIRE 
    1. Turn the engine switch on (IG).
    2. Turn the defogger switch ON.
    3. Check the voltage at the center of each defogger wire, as shown below.

      Standard voltage 

      VOLTAGE SPECIFICATION TABLE

      Voltage Criteria
      Approx. 5 V Wire Is not broken
      Approx. 10 or 0 V Wire is broken

      HINT:

      If there is approximately 10 V, the wire may be faulty between the center of the wire and the wire end on the battery side. If there is no voltage, the wire may be faulty between the center of the wire and the wire end on the ground side.

      NOTE: When measuring voltage, wrap a piece of tin foil around the tip of the negative tester probe and press the foil against the wire with your finger, as shown below.
      Fig 4: Checking Voltage At Center Of Defogger Wire
      G04952248Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    4. Place the voltmeter's positive (+) lead against the defogger wire on the battery side.
    5. Place the voltmeter's negative (-) lead with the foil strip against the wire on the ground side.
    6. Slide the positive (+) lead from the battery side to the ground side.
    7. The point where the voltage drops from approximately 10 V to 0 V is where the defogger wire is broken.

      HINT:

      If the defogger wire is not broken, the voltmeter should indicate 0 V at the positive (+) end of the defogger wire and gradually increase to approximately 12 V as the meter probe is moved to the other end.

      Fig 5: Placing Voltmeter's Positive (+) Lead Against Defogger Wire On Battery Side
      G04952249Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPAIR REAR WINDOW DEFOGGER WIRE  (See REPAIR  )

    OK: Go to next step 

  10. CHECK FRONT LIGHT ECU (OPERATION) 
    1. Temporarily replace the front light ECU with a new or normally functioning one.
    2. Check that the malfunction disappears.

      OK: Malfunction disappears. 

    NG: REPLACE AIR CONDITIONING AMPLIFIER  (See REMOVAL )

    OK: REPLACE FRONT LIGHT ECU 

scientia non olet · About LEMON Manuals