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

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DESCRIPTION


  1. 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 transmission to switch to 5th or 6th gear and the engine overruns (clutch slips), this DTC is stored.

    DTC Code
    DTC Detection Condition
    Trouble Area
    P0781
    1. 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).
    1. Valve body is blocked or stuck (1-2 shift valve)
    2. Shift solenoid valve SLT remains open or closed
    3. Automatic transmission (clutch, brake, gear, etc.)

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

      ECM gear shift command
      1st
      2nd
      3rd
      4th
      5th
      6th
      Actual gear position under malfunction
      1st
      1st
      3rd
      3rd
      N*
      N*
      N*: Neutral
    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
    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 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 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 the commanded gear position are different, it will illuminate the MIL and store the DTC.

MONITOR STRATEGY


Related DTCs
P0781: Valve body / Functional check
Required sensors/Components
Valve body, Automatic transmission assembly
Frequency of operation
Continuous
Duration
Condition (A) and (B)
0.4 seconds
Condition (C)
3 seconds
Condition (D)
1 second
MIL operation
2 driving cycles
Sequence of operation
None

TYPICAL ENABLING CONDITIONS


All 
The monitor will run whenever the following DTCs are not present
P0717 (Turbine speed sensor circuit)
P0500 (Output speed sensor circuit)
P0327, P0328, P0332, P0333 (KCS sensor circuit)
Shift solenoid valve S1 circuit
Not circuit malfunction
Shift solenoid valve S2 circuit
Not circuit malfunction
Shift solenoid valve S3 circuit
Not circuit malfunction
Shift solenoid valve S4 circuit
Not circuit malfunction
Shift solenoid valve SR circuit
Not circuit malfunction
Shift solenoid valve SL1 circuit
Not circuit malfunction
Shift solenoid valve SL2 circuit
Not circuit malfunction
ECT (Engine Coolant Temperature) sensor circuit
Not circuit malfunction
ETCS (Electric Throttle Control System)
Not system down
Transmission position
"D"
Duration time from shifting "N" to "D"
4 seconds or more
ECT
40°C (104°F) or more
Spark advance from max. retard timing by KCS control
0° crankshaft angle or more
Engine
Starting
Transfer position
HIGH*

HINT:
*: Following conditions are met

Vehicle speed sensor "A" circuit
Not circuit malfunction
Output shaft speed sensor circuit
Not circuit malfunction
Transfer output speed
143 rpm or more
Transfer input speed / Transfer output speed (NO / NOtf)
0.9 or more, and less than 1.1

Condition (A) 
ECM selected gear
2nd
Vehicle speed
2 km/h (1.2 mph) or more
Output speed
2nd → 1st down-shift point or more
Throttle valve opening angle
6.6% or more at 2000 rpm
(Conditions vary with engine speed)

Condition (B) 
ECM selected gear
4th
Vehicle speed
2 km/h (1.2 mph) or more
Throttle valve opening angle
6.6% or more at 2000 rpm
(Conditions vary with engine speed)

Condition (C) 
Current ECM selected gear
5th
Last ECM selected gear
4th
Vehicle speed (During transition from 4th to 5th gear)
Less than 100 km/h (62.2 mph)

Condition (D) 
ECM selected gear
5th
Engine speed -Turbine speed (NE - NT) (After transition to 5th gear)
150 rpm or less
Vehicle speed (After transition to 5th gear)
Less than 100 km/h (62.2 mph)

TYPICAL MALFUNCTION THRESHOLDS

  1. Both of the following conditions are met: Condition (A), and Condition (B), (C) or (D)

Condition (A) 
Turbine speed / Output speed (NT / NO)
3.30 or more, and 7.50 or less
(This means actual gear is 1st)

Condition (B) 
Turbine speed / Output speed (NT / NO)
1.28 or more, and 1.53 or less
(This means actual gear is 3rd)

Condition (C) 
Turbine speed - Output speed x 4th gear ratio
(NT - NO x 4th gear ratio)
1000 rpm or more

Condition (D) 
Turbine speed - Output speed x 5th gear ratio
(NT - NO x 5th gear ratio)
1000 rpm or more

INSPECTION PROCEDURE

NOTICE:
Perform the universal trip to clear permanent DTCs (Click here).
1.CHECK DTC OUTPUT (IN ADDITION TO DTC P0781)
  1. Connect the Techstream to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the Techstream on.

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

  1. Read the DTCs using the Techstream.

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

    HINT:
    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 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.

  1. Turn the ignition switch off.

  1. Connect the Techstream to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the Techstream on.

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

  1. According to the display on the Techstream, perform the Active Test.

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

    Engine and ECT 
    Tester Display
    Test Part
    Control Range
    Diagnostic Note
    Control the Shift Position
    Operate shift solenoid valves and set each shift position
    1. Press "→" button: Shift up
    2. Press "←" button: Shift down
    Possible to check operation of the shift solenoid valves.
    [Vehicle Condition]
    50 km/h (30 mph) or less

    HINT:
    1. This test can be conducted when the vehicle speed is 50 km/h (30 mph) or less.
    2. The 4th to 5th and 5th to 6th up-shifts must be performed with the accelerator pedal released.
    3. The 6th to 5th and 5th to 4th down-shifts 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 display on the Techstream.
    6. Gear positions in the event of a solenoid valve mechanical problem:

      Tester gear shift command
      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 Techstream command.


NG
REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY (Click here)
OK


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

NOTICE:
  1. Perform the test while the ATF temperature is 50 to 80°C (122 to 176°F).
  2. Be careful to prevent the hose of SST from interfering with the exhaust pipe.
  3. 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.


    C210149E02
  1. Remove the test plug from the center of the right side of the transmission case and connect SST.

SST
09992-00095   (09992-00231, 09992-00271)
  1. Connect the Techstream to the DLC3.

  1. Start the engine and warm it up.

  1. Measure the line pressure with SST.

  1. Turn the Techstream on.

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

  1. According to the display on the Techstream, perform the Active Test.

  1. 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

    HINT:
    1. OFF: Line pressure up (when Active Test "Activate the Solenoid (SLT)" is performed, ECM commands SLT solenoid to turn off)
    2. ON: No action (normal operation)
    [Vehicle Condition]
    1. Vehicle stopped
    2. Engine idling

    HINT:
    *: 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.
    Text in Illustration 
    *1
    Test Plug


NG
REPLACE SHIFT SOLENOID VALVE SLT (Click here)
OK


4.CLEAR DTC AND PERFORM RUNNING TEST
  1. Clear the DTC (Click here).

  1. Check for 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