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Vehicle Speed Signal Circuit between Navigation ECU and Combination Meter: Wiring Diagram

WARNING: This page is about a different car, the 2006 Lexus RX 400h. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Vehicle Speed Signal Circuit - Wiring Diagram
G04115852Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  1. CHECK OPERATION OF SPEEDOMETER 
    1. Drive the vehicle and check if the function of the speedometer in the combination meter is normal.

      OK: Actual vehicle speed and the speed indicated on the speedometer are the same. 

      HINT:

      The vehicle speed sensor is functioning normally when the indication on the speedometer is normal.

    NG: GO TO  COMBINATION METER 

    OK: GO TO NEXT STEP. 

  2. INSPECT NAVIGATION ECU 
    1. Disconnect the navigation ECU connector N3.
    2. Measure voltage.
      1. Jack up either one of the drive wheels.
      2. Move the shift lever to the neutral position.
      3. Turn the ignition switch to the ON position.
        Fig 2: Identifying ECU Connector N3
        G04115853Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      4. Measure the voltage between terminal SPD of the navigation ECU and body ground when the drive wheels are turned slowly.

        OK: Voltage pulses as shown in the illustration. 

    OK: REPLACE NAVIGATION ECU 

    Fig 3: View Of Voltage Pulses/Blinking Pattern
    G04050156Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: GO TO NEXT STEP. 

  3. CHECK HARNESS AND CONNECTOR (COMBINATION METER - NAVIGATION ECU) 
    1. Disconnect the navigation ECU connector N3 and combination meter connector C8.
    2. Measure the resistance according to the value(s) in the table below.

      Resistance 

      CONNECTOR TERMINAL RESISTANCE SPECIFICATION

      Tester connection Condition Specified condition
      SPD - C8-6 Ignition switch OFF Below 1 Ω

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Fig 4: Identifying ECU Connector N3 And Combination Meter Connector C8
    G04115855Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: GO TO NEXT STEP. 

  4. CHECK HARNESS AND CONNECTOR (COMBINATION METER - NAVIGATION ECU) 
    1. Disconnect the navigation ECU connector N3 and combination meter connector C8.
    2. Measure the resistance according to the value(s) in the table below.

      Resistance 

      CONNECTOR TERMINAL RESISTANCE SPECIFICATION

      Tester connection Condition Specified condition
      SPD - Body ground Ignition switch OFF 10 kΩ or higher
      Fig 5: Identifying ECU Connector N3 And Combination Meter Connector C8
      G04115856Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      HINT:

      If the resistance between terminal SPD and body ground is less than 10 kΩ, there may be a short in a wire harness, connector, or ECU.

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OR EACH ECU 

    OK: REPLACE COMBINATION METER 

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