P0781 Error Code Diagnostic Procedure

DESCRIPTION

  1. The 1-2 shift valve performs shifting to 1st gear and other gears.
    C159070E01



    DTC Code DTC Detection Condition Trouble Area
    P0781 The gear required by the TCM does not match the actual gear when driving (2 trip detection logic).
    1. Valve body is blocked up or stuck (1-2 shift valve)
    2. Shift solenoid valve SLT remains open or closed
    3. Automatic transmission (clutch, brake or gear, etc.)

MONITOR DESCRIPTION

This DTC indicates that the 1-2 shift valve in the valve body is locked in the direction that the spring compresses.
The TCM commands gear shifts by turning the shift solenoid valves ON/OFF and controls the oil pressure applied to the valves in the valve body.
The TCM calculates the actual transmission gear by comparing the signals from the input speed sensor NT and the output speed sensor SP2. The TCM can detect mechanical problems in the shift solenoids, valve body and automatic transmission (clutch, brake, gear, etc.). If the TCM detects that the actual gear position and the commanded gear position are different, it will illuminate the MIL and store the DTC.

INSPECTION PROCEDURE

1.CHECK DTC OUTPUT (IN ADDITION TO DTC P0781)
  1. Connect the intelligent tester to the DLC3.
  1. Turn the ignition switch to ON.
  1. Turn the intelligent tester on.
  1. Enter the following menus: Powertrain / ECT / Trouble Codes.
  1. Read the DTCs using the tester.

    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
A

 

2.PERFORM ACTIVE TEST USING INTELLIGENT TESTER (RUNNING TEST)

CAUTION:

This test should always be performed with at least 2 people.
NOTICE:
  1. Perform the test at the normal operating ATF temperature: 50 to 80°C (122 to 176°F).
  2. Perform the test with the A/C turned off.
HINT:
Using the intelligent tester 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. Connect the intelligent tester to the DLC3.
  1. Clear the DTC .
  1. Warm up the engine.
  1. Enter the following menus: Powertrain / ECT / Active Test.
  1. According to the display on the tester, perform 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 .

    ECT 
    Tester Display Test Part Control Range Diagnostic Note
    Control the Shift Position Operate shift solenoid valve and set each shift position
    1. Press “→” button: Shift up
    2. Press “←” button: Shift down
    		 It is possible to check the operation of the shift solenoid valves.
    [Vehicle Condition]
    The vehicle speed is 50 km/h (31 mph) or less.

     

    HINT:
    1. This test can be conducted when the vehicle speed is 50 km/h (31 mph) or less.
    2. The 4th to 5th up-shift must be performed with the accelerator pedal released.
    3. The 5th to 4th down-shift 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 TCM is shown in the Data List display on the tester.

     

    OK:
    Gear position changes in accordance with the tester command.
NG
REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY
OK

 

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

NOTICE:

  1. Perform the test at the normal operating ATF temperature: 50 to 80°C (122 to 176°F).
  2. Be careful to prevent SST hose from interfering with the exhaust pipe.
  3. Perform the test with the A/C turned off.
HINT:
Using the intelligent tester 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.
C159068E01
  1. Remove the test plug on the transmission case center right side and connect SST.
  1. Connect the intelligent tester to the DLC3.
  1. Start the engine and warm it up.
  1. Measure the line pressure with SST.
  1. Turn the intelligent tester on.
  1. Enter the following menus: Powertrain / ECT / Active Test.
  1. According to the display on the tester, perform the Active Test.
  1. Measure the line pressure.

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

    HINT:
    1. OFF: Line pressure up (when Active Test “Activate the Solenoid (SLT)” is performed, TCM commands shift solenoid valve SLT to turn OFF)
    2. ON: No action (normal operation)

     

    		 [Vehicle Condition]

    1. The vehicle is stopped.
    2. The engine is 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 as well. 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
OK

 

4.CLEAR DTC AND PERFORM RUNNING TEST
  1. Clear the DTC .
  1. Check for DTC again after conducting the Monitor Drive Pattern.
    OK:
    No DTC output
NG
REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY
OK
END
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