AUTOMATIC TRANSMISSION SYSTEM, Diagnostic DTC:P0781

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

SYSTEM DESCRIPTION

The 1-2 shift valve performs shifting to 1st gear and other gears.

DTC No. DTC Detection Condition Trouble Area
P0781

1-2 shift valve malfunction:

Shifting to 2nd and 4th gears is impossible. When the ECM directs the gearshift to switch to 5th or 6the gear, the engine overruns (clutch slips). (2-trip detection logic*1, 1-trip detection logic*2)

(a) and (b), or (a) and (c)

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

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

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

  • Shift solenoid valve SLT remains open or closed

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

  • Automatic transmission (clutch, brake or 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 ↑ 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* ↑ 3rd 3rd 3rd

*: 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 direction the spring compresses.

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

INSPECTION PROCEDURE

PROCEDURE


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


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG) position and push the GTS main switch ON.

    3. When you use GTS:

      Select the item "Powertrain / Engine and ECT / Trouble Codes".

    4. Read the DTCs using the GTS.

      Result
      Display (DTC output) Proceed to
      Only "P0781" is output A
      "P0781" and other DTCs 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

    Tech Tips

    Using the GTS to perform Active Test 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. Warm up the engine.

    2. Turn the engine switch off.

    3. Connect the GTS to the DLC3.

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

    5. Turn the GTS on.

    6. Select the item "Powertrain / Engine and ECT / Active Test".

    7. 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.

      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]


      • IDL: ON (4th, 5th and 6th)

      • Less than 50 km/h (31 mph)

      [Others]


      • Press "→" button: Shift up

      • Press "←" button: Shift down

      		 Possible to check the operation of the shift solenoid valves.

      Tech Tips


      • This test can be conducted when the vehicle speed is 50 km/h (31 mph) or less.

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

      • The 6th to 5th and 5th to 4th down-shiftings 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 (Shift Status) display on the GTS.

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

        GTS command gear shift 1st 2nd 3rd 4th 5th 6th
        Actual gear position under malfunction ↑ 1st ↑ 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 at the normal operating ATF (Automatic Transmission Fluid) temperature: 50 to 80°C (122 to 176°F)

    • 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.

    Tech Tips

    Using the GTS to perform Active Test 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. Turn the engine switch off.

    2. Lift the vehicle up.

    3. A01FEXZE01

      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 chock the 4 wheels.

    6. Connect the GTS to the DLC3.

    7. Start the engine.

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

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

    10. Turn the GTS on.

    11. Select the item "Powertrain / Engine and ECT / Active Test".

    12. According to the display on the GTS, perform the "Active Test".

    13. 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]


      • Vehicle Stopped.

      • IDL: ON

      Tech Tips

      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.

      Tech Tips

      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 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

    NG

    REPAIR OR REPLACE AUTOMATIC W/TRANSFER TRANSMISSION ASSEMBLY Click here

    OK

    END