AUTOMATIC TRANSMISSION SYSTEM, Diagnostic DTC:P0729

DTC Code DTC Name
P0729 Gear 6 Incorrect Ratio

SYSTEM DESCRIPTION

The TCM uses signals from the output speed sensor SP2 and input speed sensor NT to detect the actual gear position (1st, 2nd, 3rd, 4th, 5th or 6th gear). Then the TCM compares the actual gear with the shift schedule in the TCM memory to detect mechanical problems of the shift solenoid valves, valve body or automatic transmission (clutch, brake or gear, etc.).

DTC No.

DTC Detection Condition


  1. Diagnosis Condition

  2. Malfunction Status

  3. Malfunction Time

  4. Other

 Trouble Area
P0729

  1. While driving with the shift lever in D, the ATF temperature 20°C (68°F) or more, and coolant temperature 40°C (104°F) or more. (However, abnormalities with the shift solenoid valve S1, S2, S3, S4, SR, SL1, SL2, SLT), input speed sensor NT, output speed sensor SP2, park/neutral position switch, CAN bus, ECM communication, coolant temperature sensor, air flow sensor, electronically control throttle, and accelerator pedal sensor are not detected)

  2. If any of the following conditions are met:


    1. When the TCM commands shifting to 5th, the actual gear position is also switched to 5th.

    2. When the TCM commands 6th gear, the actual position is switched to 4th.

  3. -

  4. 1-trip detection logic

  • Transmission valve body assembly

  • Shift solenoid valve SLT

Tech Tips


  • Gear positions in the event of a solenoid valve mechanical problem:

    TCM command gearshift 1st 2nd 3rd 4th 5th 6th
    Actual gear position under malfunction ↑ ↑ ↑ ↑ ↑ 4th

  • Gear position during fail-safe operation:

    If any malfunction is detected, the TCM changes into the fail-safe mode to shift into the gear positions as shown in the table below.

    Gear position under normal conditions 1st 2nd 3rd 4th 5th 6th
    Actual gear position under fail-safe mode ↑ ↑ ↑ 4th 5th 5th

MONITOR DESCRIPTION

The TCM commands gear shifts by turning the shift solenoid valves "ON/OFF" and switching oil pressure to the valves in the valve body.

The DTC indicates that the sequence valve is locked in the direction the spring stretches and that shifting to the 6th gear is impossible.

CAUTION / NOTICE / HINT

Note

Perform the universal trip to clear permanent DTCs Click here.

PROCEDURE


  1. CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P0729)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch ON and push the GTS main switch ON.

    3. Read the DTCs using the GTS Click here.

      Result
      Display (DTC output) Proceed to
      Only "P0729 and P2714" are output A
      "P0729 and P0714" and other DTCs B

    B

    GO TO DTC CHART Click here

    A

  2. CHECK THE GEAR POSITION


    1. Drive the vehicle with shift lever in the M.

    2. Check the shift position.

      TCM gearshift 1st 2nd 3rd 4th 5th 6th
      Actual gear position under malfunction ↑ ↑ ↑ ↑ ↑ 4th

      Tech Tips


      • Perform the test at the normal operating ATF (Automatic Transmission Fluid) temperature: 60 to 90°C (140 to 194°F)

      • Perform under condition that A/C is OFF.

      OK
      Gear position changes.

    NG

    REPLACE TRANSMISSION VALVE BODY ASSEMBLY Click here

    OK

  3. HYDRAULIC TEST

    A004JY3E03
    Text in Illustration
    *1 SST *2 Test Plug

    Note


    • Perform the test at the normal operating ATF (Automatic Transmission Fluid) temperature: 60 to 90°C (140 to 194°F)

    • The line pressure test should always be carried out in pairs. One technician should observe the conditions of wheels or wheel stoppers outside the vehicle while the other is performing the test.

    • Be careful to prevent SST hose from interfering with the exhaust pipe.

    • This Check must be conducted after checking and adjusting engine.

    • Perform under condition that A/C is OFF.

    • When conducting stall test, do not continue more than 5 seconds.


    1. Warm up the ATF (Automatic Transmission Fluid).

    2. Lift the vehicle up.

    3. Remove the test plug on the transmission case center right side and connect SST.

      SST
      09992-00095   ( 09992-00231, 09992-00271 )

    4. Lower the vehicle.

    5. Fully apply the parking brake and check the 4 wheels.

    6. Start the engine and check idling speed.

    7. Keep your left foot pressing firmly on the brake pedal and shift into D position.

    8. Measure the line pressure when the engine is idling.

    9. Depress the accelerator pedal all the way down. Quickly read the highest line pressure when engine speed reaches stall speed.

    10. In the same manner, do the test in R position.

      Specified line pressure:
      Condition

      D position kPa (kgf / cm2, psi)

      R position kPa (kgf / cm2, psi)
      Idling

      350 to 430 kPa

      (3.6 to 4.4 kgf/cm2, 51 to 62 psi)

      760 to 950 kPa

      (7.7 to 9.7 kgf/cm2, 110 to 138 psi)
      Stall test

      1200 to 1380 kPa

      (12.5 to 14.0 kgf/cm2, 174 to 200 psi)

      1410 to 1630 kPa

      (14.4 to 16.6 kgf/cm2, 204 to 236 psi)

    NG

    REPLACE SHIFT SOLENOID VALVE SLT Click here

    OK

  4. CLEAR THE DTC AND RUNNING TEST


    1. Clear the DTC, and check DTC again after conducting the "MONITOR DRIVE PATTERN FOR ECT TEST" Click here.

      OK
      No DTC code

    OK

    END

    NG

    REPLACE TRANSMISSION VALVE BODY ASSEMBLY Click here