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Home >> Nissan-Datsun >> 2004 >> Altima S, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 896 (Continuously Variable Transmission (CVT)) >> DTC P0840 Transmission Fluid Pressure Sensor A Circuit (Sec Pressure Sensor) >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2007 Nissan Maxima. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK INPUT SIGNAL 

    With CONSULT-II 

    1. Start engine.
    2. Select "ECU INPUT SIGNALS" in "DATA MONITOR" mode for "TRANSMISSION" with CONSULT-II.
    3. Start vehicle and read out the value of "SEC HYDR SEN".
      SEC HYDR SEN DISPLAY VALUE

      Item name Condition Display value (Approx.)
      SEC HYDR SEN "N" position idle 0.8 - 1.0 V
    Fig 1: CONSULT-II Display - DATA MONITOR
    G04916087Courtesy of NISSAN MOTOR CO., U.S.A.

    Without CONSULT-II 

    1. Start engine.
    2. Check voltage between TCM connector terminal and ground.
      VOLTAGE REFERENCE CHART

      Name Connector Terminal Condition Voltage (Approx.)
      Transmission fluid pressure sensor A (Secondary pressure sensor) F57 37 - Ground "N" position idle 1.0 V
      Fig 2: Checking Voltage Between TCM Connector Terminal And Ground
      G04916146Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: GO TO  5.

    NG: GO TO  2.

  2. CHECK SENSOR POWER AND SENSOR GROUND 
    1. Turn ignition switch ON. (Do not start engine)
    2. Check voltage between TCM connector terminals.
      SENSOR POWER AND SENSOR GROUND

      Item Connector Terminal Data (Approx.)
      TCM connector F57 46 - 42 5.0 V
      Fig 3: Checking Voltage Between TCM Connector Terminals
      G04916147Courtesy of NISSAN MOTOR CO., U.S.A.

      OK or NG 

      OK: GO TO  4.

      NG: GO TO  3.

    3. CHECK HARNESS BETWEEN TCM AND CVT UNIT HARNESS CONNECTOR (SENSOR POWER AND SENSOR GROUND) 
      1. Turn ignition switch OFF.
      2. Disconnect TCM connector and CVT unit harness connector.
      3. Check continuity between TCM connector terminals and CVT unit harness connector terminals.
        CONTINUITY REFERENCE

        Item Connector Terminal Continuity
        TCM F57 42 Yes
        CVT unit harness connector F30 19
        TCM F57 46 Yes
        CVT unit harness connector F30 20
        Fig 4: Checking Harness Between TCM And CVT Unit Harness Connector (Sensor Power And Sensor Ground)
        G04916082Courtesy of NISSAN MOTOR CO., U.S.A.
      4. If OK, check harness for short to ground and short to power.
      5. Reinstall any part removed.

      OK or NG 

      OK: Replace TCM. Refer to "PRECAUTIONS FOR TCM AND CVT ASSEMBLY REPLACEMENT ".

      NG: Repair open circuit or short to ground or short to power in harness or connectors.

    4. CHECK HARNESS BETWEEN TCM AND TRANSMISSION FLUID PRESSURE SENSOR A (SECONDARY PRESSURE SENSOR) 
      1. Turn ignition switch OFF.
      2. Disconnect TCM connector and CVT unit harness connector.
      3. Check continuity between TCM connector terminal and CVT unit harness connector terminal.
        TCM AND TRANSMISSION FLUID PRESSURE SENSOR A (SECONDARY PRESSURE SENSOR)

        Item Connector Terminal Continuity
        TCM F57 37 Yes
        CVT unit harness connector F30 23
      4. If OK, check harness for short to ground and short to power.
      5. Reinstall any part removed.

      OK or NG 

      OK: GO TO  5.

      NG: Repair open circuit or short to ground or short to power in harness or connectors.

      Fig 5: Checking Harness Between TCM And Transmission Fluid Pressure Sensor (Secondary Pressure Sensor)
      G04916149Courtesy of NISSAN MOTOR CO., U.S.A.
    5. CHECK DTC 

      Perform "DTC Confirmation Procedure". Refer to "DTC CONFIRMATION PROCEDURE ".

      OK or NG 

      OK: INSPECTION END 

      NG: GO TO  6.

    6. CHECK TCM 
      1. Check TCM input/output signals. Refer to "TCM INPUT/OUTPUT SIGNAL REFERENCE VALUES ".
      2. If NG, re-check TCM pin terminals for damage or loose connection with harness connector.

      OK or NG 

      OK: Replace the transaxle assembly. Refer to "REMOVAL AND INSTALLATION ".

      NG: Repair or replace damaged parts.