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Tachometer Malfunction: Wiring Diagram

Fig 1: Tachometer - Wiring Diagram
G04050020Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  1. PERFORM ACTIVE TEST BY INTELLIGENT TESTER 
    1. Connect the intelligent tester to the DLC3.
    2. Engine switch on (IG).
    3. Turn the tester ON.
    4. Enter the following menus: DIAGNOSIS / OBD/MOBD / METER / ACTIVE TEST.
    5. Check the values by referring to the table below.

    METER: 

    METER DIAGNOSTIC REFERENCE

    Item Test Details Diagnostic Note
    TACHO METER 0, 1,000, 2,000, 3,000, 4,000, 5,000, 6,000, 7,000, 8,000 (rpm) -

    OK: 

    Needle indication is normal. 

    NG : REPLACE COMBINATION METER ASSEMBLY 

    OK : Go To Next Step 

  2. READ VALUE OF INTELLIGENT TESTER (ENGINE SPEED SIGNAL) 
    1. Connect the intelligent tester to the DLC3.
    2. Engine switch on (IG).
    3. Turn the tester ON.
    4. Enter the following menus: DIAGNOSIS / OBD/MOBD/ METER / DATA LIST.
    5. Check the values by referring to the table below.

    METER: 

    METER DISPLAY DIAGNOSTIC REFERENCE

    Item Measurement Item/Range (Display) Normal Condition Diagnostic Note
    TACHO METER Engine speed/Min.: 0 rpm, Max.: 12,750 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 step 3 

    OK : REPLACE COMBINATION METER ASSEMBLY 

  3. READ VALUE OF INTELLIGENT TESTER (ENGINE SPEED SIGNAL) 
    1. Connect the intelligent tester to the DLC3.
    2. Engine switch on (IG).
    3. Turn the tester ON.
    4. Enter the following menus: DIAGNOSIS / OBD/MOBD / ENGINE / DATA LIST.
    5. Check the values by referring to the table below.

    ENGINE: 

    ENGINE DISPLAY DIAGNOSTIC REFERENCE

    Item Measurement Item/Range (Display) Normal Condition Diagnostic Note
    ENGINE SPD Engine speed/Min.: 0 rpm, Max.: 12,750 rpm Almost same as actual engine speed (When engine is running) -

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

    Standard resistance 

    STANDARD RESISTANCE SPECIFICATION

    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
    Fig 2: Identifying A6 And J34 Connectors Terminals
    G04050021Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG : REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK : Go To Next Step 

  5. INSPECT COMBINATION METER ASSEMBLY 
    1. Check the input signal waveform.
      1. Remove the combination meter with the connector still connected.
      2. Connect the oscilloscope to the terminal J34-16 (S) and body ground.
      3. Start the engine.
        Fig 3: Connecting Oscilloscope To Terminal J34-16 (S) And Body Ground
        G04050022Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      4. Check the signal waveform according to the condition(s) in the table below.
    ITEM CONDITION REFERENCE CHART

    Item Condition
    Tool setting 5 V/DIV., 10 ms./DIV.
    Vehicle condition Engine idle speed
    Fig 4: Signal Waveform Graph
    G04050023Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: 

    The waveform is displayed as shown in the illustration. 

    OK : REPLACE COMBINATION METER ASSEMBLY 

    NG : REPLACE ECM 

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