DTC    P0729    Gear 6 Incorrect Ratio

for Preparation Click here


SYSTEM DESCRIPTION

The ECM 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 ECM compares the actual gear with the shift schedule in the ECM memory to detect mechanical problems of the shift solenoid valves, valve body or automatic transmission (clutch, brake or gear, etc.).
G023424E02

DTC No.
DTC Detecting Condition
Trouble Area
P0729
  1. 6th gearshift malfunction:
    The ECM determines there is a malfunction when both of the following conditions are met. (2-trip detection logic)
    1. When the ECM directs the gearshift to switch to 5th gear, the actual gear is also shifted to 5th.
    2. When the ECM directs the gearshift to switch to 6th gear, the actual gear is shifted to 4th.
  1. Valve body is blocked up or stuck (reverse sequence valve)
  2. Shift solenoid valve SLT remains open or closed
  3. Automatic transmission (clutch, brake or gear, etc.)

HINT:
  1. Gear positions in the event of a solenoid valve mechanical problem:

    ECM command gearshift
    		1st
    		2nd
    		3rd
    		4th
    		5th
    		6th
    Actual gear position under malfunction
    		↑
    		↑
    		↑
    		↑
    		↑
    		4th
  2. Gear position during fail-safe operation:
    If any malfunction is detected, the ECM 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
    		↑
    		↑
    		↑
    		3rd
    		3rd
    		3rd


MONITOR DESCRIPTION

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

INSPECTION PROCEDURE

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

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG) position.

  1. Turn on the tester.

  1. Select the item "Power train / ECT / DTC / Current or Pending".

  1. Read the DTCs using the intelligent tester.

    Result:

    Display (DTC output)
    		Proceed to
    Only "P0729" is output
    		A
    "P0729" and other DTCs
    		B

    HINT:
    If any other codes besides "P0729" are output, perform troubleshooting for those DTCs first.



B
GO TO DTC CHART
A


2.PERFORM ACTIVE TEST BY INTELLIGENT TESTER

HINT:
Performing the intelligent tester Active Test allows relay, Vacuum Switching Valve (VSV), actuator and other items to be operated without removing any parts. Performing the Active Test early in troubleshooting is one way to shorten labor time.
The Data List can be displayed the Active Test.

  1. Warm up the engine.

  1. Turn the engine switch off.

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG) position.

  1. Turn on the tester.

  1. Select the item "Enter / Power train / ECT / Active Test".

  1. Follow the instructions on the tester and read the Active Test.

    HINT:
    While driving, the shift position can be forcibly changed with the intelligent tester.
    Comparing the shift position commanded by the ACTIVE TEST with the actual shift position enables you to confirm the problem (Click here).


    Item
    		Test Details
    		Diagnostic Note
    Control the Shift Position
    		[Test Details]
    Operate the shift solenoid valve and set the each shift position by yourself.
    [Vehicle Condition]
    1. IDL: ON
    2. Less than 50 km/h (31 mph)
    [Others]
    1. Press "→" button: Shift up
    2. Press "←" button: Shift down
    		Possible to check the operation of the shift solenoid valves.

    HINT:
    1. This test can be conducted when the vehicle speed is 50 km/h (31 mph) or less.
    2. The 4th to 5th and 5th to 6th up-shiftings must be performed with the accelerator pedal released.
    3. The 6th to 5th and 5th to 4th down-shiftings must be performed with the accelerator pedal released.
    4. Do not operate the accelerator pedal for at least 2 seconds after shifting and do not shift successively.
    5. The shift position commanded by the ECM is shown in the DATA LIST (Shift Status) display on the intelligent tester.
    6. Gear positions in the event of a solenoid valve mechanical problem:

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

    OK:
    Gear position changes in accordance with the tester command.



NG
REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY
OK


3.INSPECT SHIFT SOLENOID VALVE SLT


    G020767E08

  1. Remove the shift solenoid valve SLT.

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

    Resistance:
    Tester Connection
    		Specified Condition
    20°C (68°F)
    1 - 2
    		5.0 to 5.6 Ω

  1. Connect the positive (+) lead with a 21 W bulb to terminal 2 and the negative (-) lead to terminal 1 of the solenoid valve connector, then check the movement of the valve.

    OK:
    The solenoid makes an operating sound.



NG
REPLACE SHIFT SOLENOID VALVE SLT
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



NG
REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY
OK

END