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Tachometer Malfunction: Procedure

  1. PERFORM ACTIVE TEST USING TECHSTREAM (TACHOMETER OPERATION) 
    1. Connect Techstream to the DLC3.
    2. Ignition 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 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. Start the engine.
    3. Turn the tester on.
    4. Enter the following menus: Body Electrical / Combination Meter / Data List.
    5. Check the values by referring to 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 Techstream to the DLC3.
    2. Ignition 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 ENGINE CONTROL SYSTEM  SFI SYSTEM 

    OK: Go to next step 

  4. CHECK HARNESS AND CONNECTOR (ECM - COMBINATION METER) 
    1. Disconnect the E30 and A55 connectors.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection (Symbols) Condition Specified Condition
      E30-31 (S) - A55-15 (TACH) Always Below 1 Ω
      E30-31 (S) - Body ground Always 10 kΩ or higher

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  5. INSPECT ECM (INPUT WAVEFORM) 
    1. Check the input waveform.
      Fig 1: Identifying E30 Connector Terminals And View Of Input Waveform Graph
      GTY302192Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      1. Disconnect the E30 connector.
      2. Reconnect the A55 connector.
      3. Connect the oscilloscope to the terminals E30-31 (S) and body ground.
      4. Start the engine.
      5. Check the input waveform according to the condition(s) in the table below.
        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.

    NG → REPLACE ECM 

    OK → REPLACE COMBINATION METER ASSEMBLY 

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