Home › Drivetrain › Automatic Transmission/Transaxle › AB60F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM
Last Modified: 11-27-2007 1.6 C
Service Category: Drivetrain Section: Automatic Transmission/Transaxle
Model Year: 2008 Model: LX570 Doc ID: RM000000XP103CX
Title: AB60F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: DESCRIPTION (2008 LX570)

DTC

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



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.)

HINT:

  • Gear positions in the event of a shift 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

    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 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 with the shift solenoid valves, 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/Rationality check

Required sensors/Components

Valve body, Automatic transmission assembly

Frequency of operation

Continuous

Duration

Condition (A) and (B)

0.4 sec.

Condition (C)

3 sec.

Condition (D)

1 sec.

MIL operation

2 driving cycles

Sequence of operation

None

TYPICAL ENABLING CONDITIONS

ALL

The monitor will run whenever the following DTCs are not stored

P0500 (VSS)

P0748 - P0798 (Trans solenoid (range))

Turbine speed sensor circuit

Not circuit malfunction

Output speed sensor circuit

Not circuit malfunction

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

KCS sensor circuit

Not circuit malfunction

ETCS (Electric Throttle Control System)

Not system down

Transmission position

D

Duration time from shifting N to D

4 sec. 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

Transfer position

HIGH*

HINT:

*: Following conditions met

Vehicle speed sensor 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 (1.3 mph) or more

Output speed

2nd → 1st down-shift point or more

Throttle valve opening angle

9% or more at 2000 rpm

(Conditions vary with engine speed)

Condition (B)

ECM selected gear

4th

Vehicle speed

2 km/h (1.3 mph) or more

Throttle valve opening angle

9% 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 (62.1 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 (62.1 mph)

TYPICAL MALFUNCTION THRESHOLDS

When both of the following conditions are met: Condition (A), and Condition (B), (C) or (D)

Condition (A)

Turbine speed/Output speed (NT/NO)

3.11 or more, and 7.58 or less

(This means actual gear is 1st)

Condition (B)

Turbine speed/Output speed (NT/NO)

1.24 or more, and 1.49 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

PROCEDURE

1.

CHECK DTC OUTPUT (IN ADDITION TO DTC P0781)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(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.

A

2.

PERFORM ACTIVE TEST USING TECHSTREAM (RUNNING TEST)

CAUTION:

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

NOTICE:

  • Perform the test at the normal operating ATF temperature: 50 to 80°C (122 to 176°F).
  • Perform the test with the A/C turned 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.

(a) Connect the Techstream to the DLC3.

(b) Clear the DTC AB60F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: DTC CHECK / CLEAR (2008 LX570) .

(c) Warm up the engine.

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

(e) According to the display on the Techstream, perform the Active Test.

HINT:

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

Comparing the shift position commanded by the Active Test with the actual shift position enables you to confirm the problem AB60F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: FAIL-SAFE CHART (2008 LX570) .

Engine and ECT

Tester Display

Test Part

Control Range

Diagnostic Note

Control the Shift Position

Operate shift solenoid valve and set each shift position
  • Press "→" button: Shift up
  • 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:

  • 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-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 shift solenoid valve mechanical problem:

    Techstream 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.

OK

3.

PERFORM ACTIVE TEST USING TECHSTREAM (SHIFT SOLENOID VALVE SLT)

NOTICE:

  • Perform the test at the normal operating ATF temperature: 50 to 80°C (122 to 176°F).
  • Be careful to prevent SST hose from interfering with the exhaust pipe.
  • Perform the test with the A/C turned 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.

(a) Remove the test plug on the transmission case center right side and connect SST.

SST: 09992-00095

09992-00231

09992-00271

(b) Connect the Techstream to the DLC3.

(c) Start the engine and warm it up.

(d) Measure the line pressure with SST.

(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.

(h) Measure the line pressure.

Engine and 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:

  • OFF: Line pressure up (when Active Test "Activate the Solenoid (SLT)" is performed, ECM commands shift solenoid valve SLT to turn OFF)
  • ON: No action (normal operation)

[Vehicle Condition]

  • The vehicle is stopped.
  • 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 AB60F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: HYDRAULIC TEST (2008 LX570) 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.

OK

4.

CLEAR DTC AND PERFORM RUNNING TEST

(a) Clear the DTC AB60F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: DTC CHECK / CLEAR (2008 LX570) .

(b) Check for DTC again after conducting the Monitor Drive Pattern AB60F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: MONITOR DRIVE PATTERN (2008 LX570) .

OK:

No DTC output.

OK