LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2010 >> LS 460L AWD >> Repair and Diagnosis >> Body & Frame >> Windows >> Windshield / WINDOWGLASS (Diagnostics) >> Windshield Deicer System >> Windshield Deicer does not Operate >> Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Windshield Deicer does not Operate: Procedure

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

      OK

      Engine starts normally.

    NG → See step   11 

    OK: Go to next step 

  2. PERFORM ACTIVE TEST USING TECHSTREAM (DEICER RELAY) 
    1. Select the Active Test, using the Techstream to generate a control command, and then check that the windshield deicer operates.
      AIR CONDITIONER

      Tester Display Test Part Control Range Diagnostic Note
      Deicer Relay (Front) Deicer relay operation OFF / ON -
      RESULT

      Result Proceed to
      Windshield deicer operates normally (w/ Display and Navigation Module Display) A
      Windshield deicer operates normally (w/o Display and Navigation Module Display) B
      Windshield deicer does not operate C

    C → See step   5 

    B → See step   4 

    A: Go to next step 

  3. CHECK DISPLAY AND NAVIGATION MODULE DISPLAY (OPERATION) 
    1. Temporarily replace the display and navigation module display with a new or normally functioning one. Refer to REMOVAL .
    2. Check that the malfunction disappears.

      OK

      Malfunction disappears.

      RESULT

      Result Proceed to
      OK (w/o Navigation System) A
      OK (w/ Navigation System [for HDD]) B
      OK (w/ Navigation System [for DVD]) C
      NG D

    D → See step   12 

    C → See step   13 

    B → See step   16 

    A → See step   15 

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

      OK

      Malfunction disappears.

    NG → See step   12 

    OK → See step   14 

  5. INSPECT FUSE (DEICER) 
    1. Remove the DEICER fuse from the engine room No. 2 relay block.
    2. Measure the resistance of the fuse.

      Standard resistance

      Tester Connection Condition Specified Condition
      DEICER fuse Always Below 1 Ω

    NG → REPLACE FUSE 

    OK: Go to next step 

  6. INSPECT DEICER RELAY 
    Fig 1: Identifying Deicer Relay
    GTY120672Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Remove the deicer relay from the No. 3 relay block.
    2. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester Connection Condition Specified Condition
      3 - 5 When battery voltage is not applied between terminals 10 kΩ or higher
      When battery voltage is applied to terminals 1 and 2 Below 1 Ω

    NG → REPLACE DEICER RELAY 

    OK: Go to next step 

  7. CHECK HARNESS AND CONNECTOR (DEICER RELAY - FRONT LIGHT ECU AND BATTERY) 
    Fig 2: Identifying A51 Front Light ECU Connector
    GTY118126Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Remove the deicer 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

      Tester Connection Switch Condition Specified Condition
      Deicer relay terminal 1 - Body ground Engine switch on (IG) 11 to 14 V
      Deicer 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

      Tester Connection Condition Specified Condition
      Deicer relay terminal 2 - A51-13 (FDEF) Always Below 1 Ω

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  8. CHECK HARNESS AND CONNECTOR (DEICER RELAY - WINDSHIELD DEICER WIRE) 
    Fig 3: Identifying A30 Windshield Deicer Wire Connector
    GTY116863Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Remove the deicer relay from the No. 3 relay block.
    2. Disconnect the A30 windshield deicer wire connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester Connection Condition Specified Condition
      A30-1 (B2) - Deicer relay terminal 3 Always Below 1 Ω
      A30-2 (B) - Deicer relay terminal 3 Always Below 1 Ω
      Deicer relay terminal 3 - Body ground Always 10 kΩ or higher

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  9. CHECK HARNESS AND CONNECTOR (WINDSHIELD DEICER WIRE - BODY GROUND) 
    Fig 4: Identifying A30 Windshield Deicer Connector
    GTY121599Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect the A30 windshield deicer wire connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester Connection Condition Specified Condition
      A30-3 (E) - Body ground Always Below 1 Ω

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    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 → See step   12 

    OK → REPLACE FRONT LIGHT ECU 

  11. GO TO SMART ACCESS SYSTEM WITH PUSH-BUTTON START. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING 
  12. REPLACE AIR CONDITIONING AMPLIFIER. Refer to  REMOVAL 
  13. REPLACE DISPLAY AND NAVIGATION MODULE DISPLAY. Refer to  REMOVAL 
  14. REPLACE INTEGRATION CONTROL AND PANEL. Refer to  REMOVAL 
  15. REPLACE DISPLAY AND NAVIGATION MODULE DISPLAY. Refer to  REMOVAL 
  16. REPLACE DISPLAY AND NAVIGATION MODULE DISPLAY. Refer to  REMOVAL 
scientia non olet · About LEMON Manuals