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Home › Lexus › 2008 › SC 430 › Repair and Diagnosis › Transmission › Automatic Trans › Automatic Transaxle › Automatic Transmission System › DTC P0729: Gear 6 Incorrect Ratio › Inspection Procedure

Inspection Procedure

  1. CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P0729) 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
    5. Read the DTCs using the Techstream.

      Result 

      RESULT CHART

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

      HINT:

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

    B: GO TO DTC CHART 

    A: Go to Next Step 

  2. PERFORM ACTIVE TEST BY TECHSTREAM (RUNNING TEST) 

    HINT:

    Using the Techstream to perform Active Tests allows relays, VSVs, actuators and other items to be operated without removing any parts. This non-intrusive functional inspection can be very useful because intermittent operation may be discovered before parts or wiring is disturbed. Performing Active Tests early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Tests.

    1. Warm up the engine.
    2. Turn the ignition switch OFF.
    3. Connect the Techstream to the DLC3.
    4. Turn the ignition switch to ON.
    5. Turn the Techstream on.
    6. Enter the following menus: Powertrain / Engine and ECT / Active Test.
    7. According to the display on the Techstream, perform the Active Test.

      HINT:

      While driving, the shift position can be forcibly changed with the Techstream.

      Comparing the shift position commanded by the Active Test with the actual shift position enables you to confirm the problem (see CHECK MODE PROCEDURE  ).

      Engine and ECT 

      ACTIVE TEST

      Tester Display Test Part Control Range Diagnostic Note
      Control the Shift Position Operate shift solenoid valve and set each shift position
      • Press "→" button: Shift up
      • Press "←" button: Shift down
      		 Possible to check operation of shift solenoid valves
      [Vehicle Condition]
      50 km/h (31 mph) or less

      HINT:

      • This test can be conducted when the vehicle speed is 50 km/h (31 mph) or less.
      • The 4th → 5th and 5th → 6th up-shifts must be performed with the accelerator pedal released.
      • The 6th → 5th and 5th → 4th down-shifts must be performed with the accelerator pedal released.
      • Do not operate the accelerator pedal for at least 2 seconds after shifting and do not shift successively.
      • The shift position commanded by the ECM is shown in the Data List display on the Techstream.
      • Gear positions in the event of a solenoid valve mechanical problem:
        GEAR POSITIONS REFERENCE

        Techstream gear shift command 1st 2nd 3rd 4th 5th 6th
        Actual gear position under malfunction 1st 2nd 3rd 4th 5th 4th

        OK: 

        Gear position changes in accordance with the Techstream command. 

    NG: REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY 

    OK: Go to Next Step 

  3. PERFORM ACTIVE TEST BY TECHSTREAM (SHIFT SOLENOID VALVE SLT) 
    NOTE:
    • Perform the test at the normal operating ATF temperature: 50 to 80°C (122 to 176°F).
    • Be careful to prevent SST's hose from interfering with the exhaust pipe.
    • Perform the test with the A/C OFF.

    HINT:

    Using the Techstream to perform Active Tests allows relays, VSVs, actuators and other items to be operated without removing any parts. This non-intrusive functional inspection can be very useful because intermittent operation may be discovered before parts or wiring is disturbed. Performing Active Tests early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Tests.

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

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

      Fig 1: Measuring Line Pressure With SST
      G05289558Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Connect the Techstream to the DLC3.
    3. Start the engine and warm it up.
    4. Measure the line pressure with SST.
    5. Turn the Techstream on.
    6. Enter the following menus: Powertrain / Engine and ECT / Active Test.
    7. According to the display on the Techstream, perform the Active Test.
    8. Measure the line pressure with SST.

      Engine and ECT 

      ACTIVE TEST

      Tester Display Test Part Control Range Diagnostic Note
      Control the Line Pressure Up* Operate the shift solenoid SLT and raise line pressure ON or OFF
      HINT:
      • OFF: Line pressure up (when Active Test "Control the Line Pressure Up" is performed, ECM commands SLT solenoid to turn OFF)
      • ON: No action (normal operation)
      		 [Vehicle Condition]
      • Vehicle stopped
      • Engine idling
      HINT:
      • *: Control the Line Pressure Up in the Active Test is performed to check the line pressure change by connecting SST to the automatic transmission, which is used in the HYDRAULIC TEST  .
      • The pressure values in the Active Test and Hydraulic Test are different from each other.
      • Normally, the line pressure detected in the Active Test is approximately half of the value detected in the Hydraulic Test's stall test.

      OK: 

      The line pressure changes as specified when performing the Active Test. 

    NG: REPLACE SHIFT SOLENOID VALVE SLT 

    OK: Go to Next Step 

  4. CLEAR THE DTC AND PERFORM THE RUNNING TEST 
    1. Clear the DTC, and check for DTCs again after conducting the "MONITOR DRIVE PATTERN FOR ECT TEST" (see MONITOR DRIVE PATTERN  ).

      OK: 

      No DTC code is output 

    NG: REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY 

    OK: END 

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