METER / GAUGE SYSTEM Tachometer Malfunction

DESCRIPTION

The meter CPU receives engine speed signals from the ECM in this circuit. The ECM transmits engine speed signals as pulses to the meter CPU. The meter CPU calculates the engine speed converting 4 pulses to 2 revolutions.

WIRING DIAGRAM

A0162HGE02

INSPECTION PROCEDURE

PROCEDURE


  1. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (TACHO METER OPERATION)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the intelligent tester on.

    4. Enter the following menus: Body / 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) Confirm that the vehicle is stopped, engine idling
      OK
      Tachometer indication is normal.

    NG

    REPLACE COMBINATION METER Click here

    OK

  2. READ VALUE USING INTELLIGENT TESTER (ENGINE RPM)


    1. Connect the intelligent tester to the DLC3.

    2. Engine start.

    3. Turn the intelligent tester on.

    4. Enter the following menus: Body / 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 (tachometer indication) 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.
      Result
      Result Proceed to
      The tachometer indication differs from the engine speed displayed on the intelligent tester. A
      Engine speed displayed on the intelligent tester is almost the same as the tachometer indication. B
      Both the tachometer indication and the engine speed displayed on the intelligent tester is 0. C

    B

    READ VALUE USING INTELLIGENT TESTER (ENGINE SPEED) Click here

    C

    CHECK HARNESS AND CONNECTOR (COMBINATION METER - ECM) Click here

    A

    REPLACE COMBINATION METER Click here

  3. READ VALUE USING INTELLIGENT TESTER (ENGINE SPEED)


    1. Connect the intelligent tester to the DLC3.

    2. Engine start.

    3. Turn the intelligent 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 (tachometer indication) -
      OK
      Engine speed displayed on the intelligent tester is almost the same as the tachometer indication.

    NG

    GO TO SFI SYSTEM (for 2UR-GSE) Click here

    OK

  4. CHECK HARNESS AND CONNECTOR (COMBINATION METER - ECM)


    1. A0161UVE02

      Disconnect the A5 and J34 connectors.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      A5-15 (TACH) - J34-16 (S) Always Below 1 Ω
      A5-15 (TACH) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  5. INSPECT ECM (INPUT WAVEFORM)


    1. A0161KXE02

      Check the input signal waveform.


      1. Reconnect the A5 ECM connector.

      2. Connect the oscilloscope to the terminal J34-16 (S) and body ground.

      3. Start the engine.

      4. Check the signal waveform according to the condition(s) in the table below.

        Item Condition
        Tool setting 5 V/DIV., 10 ms./DIV.
        Vehicle condition Engine idling
        OK
        The waveform is displayed as shown in the illustration.

        Tech Tips

        When the system is functioning normally, one engine revolution generates 4 pulses. As the engine speed increases, the width indicated by (A) in the illustration narrows.


    NG

    REPLACE ECM (for 2UR-GSE) Click here

    OK

    REPLACE COMBINATION METER Click here