AUTOMATIC TRANSMISSION SYSTEM (for 1UR-FE), Diagnostic DTC:P0781

DTC Code DTC Name
P0781 1-2 Shift (1-2 Shift Valve)

DESCRIPTION

The 1-2 shift valve performs shifting to 1st gear and other gears. When shifting to 2nd and 4th gears is impossible, or when the ECM directs the gearshift to switch to 5th and 6th gear and the engine overruns (clutch slips), this DTC is output.

DTC Code DTC Detection Condition Trouble Area
P0781

  • When conditions (a) and (b), or (a) and (c) are met. (2 trip detection logic)

(a) When the ECM directs the transmission to switch to 2nd gear, the actual gear is shifted to 1st.

(b) When the ECM directs the transmission to switch to 4th gear, the actual gear is shifted to 3rd.

(c) When the ECM directs the transmission to switch to 5th gear, the engine overruns (clutch slips).

  • Valve body is blocked up or stuck (1-2 shift valve)

  • Shift solenoid valve SLT remains open or closed

  • Automatic transmission (clutch, brake, gear, etc.)

Tech Tips


  • 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 1st 1st 3rd 3rd N* N*

    N*: Neutral

  • 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 1st* 1st* 3rd 3rd 3rd 3rd

1st*: Under engine braking, downshifting to 1st or 2nd gear is prohibited.

MONITOR DESCRIPTION

This DTC indicates that the 1-2 shift valve in the valve body is locked in the position in which the spring is compressed.

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 ECM calculates the actual transmission gear by comparing the signals from the input speed sensor (NT) and the output speed sensor (SP2). The ECM can detect many mechanical problems in the shift solenoids, valve body, transmission clutches, brakes, and gears. If the ECM detects that the actual gear position and commanded gear position are different, it will illuminate the MIL and store the DTC.

INSPECTION PROCEDURE

PROCEDURE


  1. CHECK DTC OUTPUT (IN ADDITION TO DTC P0781)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

    5. Read the DTCs using the GTS.

      Result
      Result Proceed to
      Only P0781 is output A
      P0781 and other DTCs are output B

      Tech Tips

      If any other codes besides P0781 are output, perform troubleshooting for those DTCs first.


    B

    GO TO DTC CHART Click here

    A

  2. PERFORM ACTIVE TEST USING GTS (RUNNING TEST)

    CAUTION:

    This test should always be performed with at least 2 people.

    Note


    • Perform the test while the ATF temperature is between 50 and 80°C (122 and 176°F).

    • Perform the test with the A/C turned off.

    Tech Tips

    Using the GTS 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 Test early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Test.


    1. Connect the GTS to the DLC3.

    2. Clear the DTC Click here.

    3. Warm up the engine.

    4. Enter the following menus: Powertrain / Engine and ECT / Active Test.

    5. According to the display on the GTS, perform the Active Test.

      Tech Tips

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

      Comparing the shift position commanded by the Active Test with the actual shift position enables you to confirm the problem Click here.

      Engine and ECT
      Tester Display Test Part Control Range Diagnostic Note
      Control the Shift Position Operate shift solenoid valves and set each shift position by yourself

      • Press "→" button: Shift up

      • Press "←" button: Shift down

      Possible to check operation of the shift solenoid valves.

      [Vehicle Condition]

      50 km/h (30 mph) or less

      Tech Tips


      • This test can be conducted when the vehicle speed is 50 km/h (30 mph) or less.

      • The 4th to 5th and 5th to 6th up-shift must be performed with the accelerator pedal released.

      • The 6th to 5th and 5th to 4th down-shift 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 GTS.

      • 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 1st 1st 3rd 3rd N* N*

        N*: Neutral

        OK
        Gear position changes in accordance with the GTS command.

    NG

    REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY Click here

    OK

  3. PERFORM ACTIVE TEST USING GTS (SHIFT SOLENOID VALVE SLT)

    Note


    • Perform the test while the ATF temperature is between 50 and 80°C (122 and 176°F).

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

    • Perform the test with the A/C off.

    Tech Tips

    Using the GTS 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. A01ENZ4E01

      Remove the test plug on the transmission case and connect SST.

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

    2. Connect the GTS to the DLC3.

    3. Start the engine and warm it up.

    4. Measure the line pressure with SST.

    5. Turn the GTS on.

    6. Enter the following menus: Powertrain / Engine and ECT / Active Test.

    7. According to the display on the GTS, perform the Active Test.

    8. Measure the line pressure.

      Engine and ECT
      Tester Display Test Part Control Range Diagnostic Note
      Activate the Solenoid (SLT)* Operate the shift solenoid SLT and raise line pressure

      ON or OFF

      Tech Tips


      • OFF: Line pressure up (when Active Test "Activate the Solenoid (SLT)" is performed, ECM commands SLT solenoid to turn OFF)

      • ON: No action (normal operation)

      [Vehicle Condition]


      • Vehicle stopped

      • Engine idling

      Tech Tips

      *: Activate the Solenoid (SLT) in the Active Test is performed to check the line pressure changes by connecting SST to the automatic transmission, which is used in the Hydraulic Test Click here as well. Please note that the pressure values in the Active Test and Hydraulic Test are different.

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

    NG

    REPLACE SHIFT SOLENOID VALVE SLT Click here

    OK

  4. CLEAR DTC AND PERFORM RUNNING TEST


    1. Clear the DTC Click here.

    2. Check the DTC again after conducting the Monitor Drive Pattern Click here.

      OK
      No DTC code output.

    NG

    REPAIR OR REPLACE AUTOMATIC TRANSMISSION ASSEMBLY Click here

    OK

    END