Dtc P0729 Gear 6 Incorrect Ratio

Transmission. Lexus Is250, Is220D. Gse20 Ale20
A960E Automatic Transmission. Lexus Is250, Is220D. Gse20 Ale20

SYSTEM DESCRIPTION

MONITOR DESCRIPTION

INSPECTION PROCEDURE

CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P0729)

PERFORM ACTIVE TEST BY INTELLIGENT TESTER

PERFORM ACTIVE TEST BY INTELLIGENT TESTER (SHIFT SOLENOID VALVE SLT)

CLEAR THE DTC AND RUNNING TEST

DTC P0729 Gear 6 Incorrect Ratio


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.).
Lexus Is250, Is220D. Gse20 Ale20.A960E Automatic Transmission.Automatic Transmission System. Dtc P0729 Gear 6 Incorrect Ratio

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 (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 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 "Powertrain / 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 / Powertrain / 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 each shift position by yourself.
    [Vehicle Condition]
    1. 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
REPLACE TRANSMISSION VALVE BODY ASSEMBLY
OK


3.PERFORM ACTIVE TEST BY INTELLIGENT TESTER (SHIFT SOLENOID VALVE SLT)
NOTICE:
  1. Perform the test at the normal operating ATF (Automatic Transmission Fluid) temperature: 50 to 80°C (122 to 176°F)
  2. Be careful to prevent SST hose from interfering with the exhaust pipe.
  3. This check must be conducted after checking and adjusting engine.
  4. Perform under condition that A/C is OFF.
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 during the Active Test.
Turn the engine switch off.

  1. Turn the engine switch off.

  1. Lift the vehicle up.



    Lexus Is250, Is220D. Gse20 Ale20.A960E Automatic Transmission.Automatic Transmission System. Dtc P0729 Gear 6 Incorrect Ratio

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

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

  1. Lower the vehicle.

  1. Fully apply the parking brake and chock the 4 wheels.

  1. Connect the intelligent tester to the DLC3.

  1. Start the engine.

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

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

  1. Turn on the intelligent tester.

  1. Select the item "Enter / Powertrain / ECT / Active Test".

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

  1. Measure the line pressure with SST.

    Item
    		Test Details
    Activate the Solenoid (SLT)*
    		[Test Details]
    Operate the shift solenoid SLT and raise the line pressure.
    [Vehicle Condition]
    1. Vehicle Stopped.
    2. IDL: ON
    HINT:
    OFF: Line pressure up (When the active test of "Activate the Solenoid (SLT)" is performed, the ECM commands the SLT solenoid to turn off).
    ON: No action (normal operation)
    *: "Activate the Solenoid (SLT)" in the ACTIVE TEST is performed to check the line pressure changes by connecting the SST to the automatic transmission, which is used in the HYDRAULIC TEST (Click here) as well.
    HINT:
    The pressure values in ACTIVE TEST and HYDRAULIC TEST are different from each other.
    OK:
    The line pressure changes as specified when performing the ACTIVE TEST.


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
REPLACE TRANSMISSION VALVE BODY ASSEMBLY
OK

END