Toyota Tundra Service Manual: 1-2 Shift (1-2 Shift Valve) (P0781)

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 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

  • 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 or stuck (1-2 shift valve)
  • Shift solenoid valve SLT remains open or closed
  • Automatic transmission (clutch, brake, gear, etc.)

HINT:

  • 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

  • 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

HINT:

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)

P0722 (Output Speed Sensor circuit)

P0710, P0712, P0713, P2740, P2742, P2743 (ATF temperature sensor circuit)

P0973, P0974 (Shift solenoid valve S1 circuit)

P0976, P0977 (Shift solenoid valve S2 circuit)

P0979, P0980 (Shift solenoid valve S3 circuit)

P0982, P0983 (Shift solenoid valve S4 circuit)

P0985, P0986 (Shift solenoid valve SR circuit)

P0748 (Shift solenoid valve SL1 circuit)

P0778 (Shift solenoid valve SL2 circuit)

P0115, P0116, P0117, P0118, P011B (ECT (Engine coolant temperature) sensor circuit)

P0327, P0328, P032C, P032D (KCS sensor circuit)

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 higher

Spark advance from max. retard timing by KCS control

0° crankshaft angle or more

Engine

Starting

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

5% or more at 2000 rpm

(Conditions vary with engine speed)

Calculated load value

7.75% or more (A/C off)

7.75% or more (A/C on)

Input speed/output speed (NT/NO)

NT: Input (Turbine) speed

NO: Internal counter shaft speed

3.30 to 7.50

or

1.91 to 2.35

or

1.28 to 1.53

or

0.93 to 1.07

or

0.65 to 0.79

or

0.51 to 0.65

Condition (B)

ECM selected gear

4th

Vehicle speed

2 km/h (1.2 mph) or more

Throttle valve opening angle

5% or more at 2000 rpm

(Conditions vary with engine speed)

Calculated load value

7.75% or more (A/C off)

7.75% or more (A/C on)

Input speed/output speed (NT/NO)

NT: Input (Turbine) speed

NO: Internal counter shaft speed

3.30 to 7.50

or

1.91 to 2.35

or

1.28 to 1.53

or

0.93 to 1.07

or

0.65 to 0.79

or

0.51 to 0.65

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

  • 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

CAUTION / NOTICE / HINT

NOTICE:

Perform the universal trip to clear permanent DTCs (See page ).

PROCEDURE

1.

CHECK DTC OUTPUT (IN ADDITION TO DTC P0781)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) 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

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.

(a) Warm up the engine.

(b) Turn the ignition switch off.

(c) Connect the Techstream to the DLC3.

(d) Turn the ignition switch to ON.

(e) Turn the Techstream on.

(f) Enter the following menus: Powertrain / Engine and ECT / Active Test.

(g) 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

  • 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

HINT:

  • 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-shifts must be performed with the accelerator pedal released.
  • The 6th to 5th and 5th to 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:

    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

OK

3.

PERFORM ACTIVE TEST USING TECHSTREAM (SHIFT SOLENOID VALVE SLT)

NG

REPLACE SHIFT SOLENOID VALVE SLT

OK

4.

CLEAR DTC AND PERFORM RUNNING TEST

OK

END

NG

REPAIR OR REPLACE AUTOMATIC TRANSMISSION ASSEMBLY

    Pressure Control Solenoid "B" Electrical (Shift Solenoid Valve SL2) (P0778)

    Transmission Component Slipping (P0894,P2714)

    See More:

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