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Home >> Lexus >> 2012 >> IS 250 Base, AWD >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Meter & Gauge System (Diagnostics & Symptom Tests) >> Meter / Gauge System >> Symptom Tests >> Tachometer Malfunction >> Procedure

Tachometer Malfunction: Procedure

  1. PERFORM ACTIVE TEST USING TECHSTREAM (TACHO METER OPERATION) 
    1. Connect Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the tester ON.
    4. Enter the following menus: Body Electrical / Combination Meter / Active Test.
    5. Check the operation by referring to the values in the table below.
      COMBINATION METER:

      Tester Display Test Part Control Range Diagnostic Note
      Tacho Meter Operation Tachometer 0, 1000, 2000, 3000, 4000, 5000, 6000, 7000 (rpm) -

      OK

      Needle indication is normal.

    NG → REPLACE COMBINATION METER ASSEMBLY 

    OK: Go to next step 

  2. READ VALUE USING TECHSTREAM (ENGINE RPM) 
    1. Connect Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the tester ON.
    4. Enter the following menus: Body Electrical / Combination Meter / Data List.
    5. Check the values by referring to the values in the table below.
      COMBINATION METER:

      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Engine Rpm Engine speed/Min.: 0 rpm, Max.: 12750 rpm Almost same as actual engine speed (When engine is running) If data received from the ECM exceeds the range that can be displayed on the meter, the meter continues to display the maximum value of the range.

      OK

      Engine speed displayed on the tester is almost the same as the actual engine speed.

    NG → See step   3 

    OK → REPLACE COMBINATION METER ASSEMBLY 

  3. READ VALUE USING TECHSTREAM (ENGINE SPEED) 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the tester ON.
    4. Enter the following menus: Powertrain / Engine and ECT / Data List.
    5. Check the values by referring to the table below.
      ENGINE AND ECT:

      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Engine Speed Engine speed/Min.: 0 rpm, Max.: 16383.75 rpm Almost same as actual engine speed (When engine is running) -

      OK

      Engine speed displayed on the tester is almost the same as the actual engine speed.

    NG → GO TO SFI SYSTEM 

    OK: Go to next step 

  4. CHECK HARNESS AND CONNECTOR (COMBINATION METER - ECM) 
    1. Disconnect the A6 and J34 connectors.
      Fig 1: Identifying A6 And J34 Connectors Terminals
      GTY150874Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester Connection Condition Specified Condition
      A6-16 (TACH) - J34-16 (S) Always Below 1 Ω
      A6-16 (TACH) - Body ground Always 10 kΩ or higher

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  5. INSPECT COMBINATION METER ASSEMBLY 
    1. Check the input signal waveform.
      Fig 2: Identifying Terminal J34-16 (S) And Body Ground
      GTY142563Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      1. Disconnect the J34 connector.
      2. Reconnect the A6 connector.
      3. Connect the oscilloscope to the terminal J34-16 (S) and body ground.
      4. Start the engine.
      5. Check the signal waveform according to the condition(s) in the table below.
        Fig 3: View Of Signal Waveform Graph
        GTY103209Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
        Item Condition
        Tool setting 5 V/DIV., 10 ms./DIV.
        Vehicle condition Engine idle speed

        OK

        The waveform is displayed as shown in the illustration.

    OK → REPLACE COMBINATION METER ASSEMBLY 

    NG → REPLACE ECM 

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