A750E AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: DESCRIPTION (2008 Sequoia)

Last Modified: 11-29-2007		1.6 C
Service Category: Drivetrain	Section: Automatic Transmission/Transaxle
Model Year: 2008	Model: Sequoia	Doc ID: RM000000XP103JX
Title: A750E AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: DESCRIPTION (2008 Sequoia)

DTC

P0781

1-2 Shift (1-2 Shift Valve)

DESCRIPTION

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

DTC No.	DTC Detection Condition	Trouble Area
P0781	Gear required by the ECM does not match the actual gear when driving. (2 trip detection logic)	Valve body is blocked up or stuck (1-2 shift valve) Shift solenoid valve SLT remains open or closed 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 ECM 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 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 mechanical problems in the shift solenoids, valve body and automatic transmission (clutch, brake, gear, etc.). 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, Speed sensor (NT), Speed sensor (SP2), Vehicle speed sensor, Throttle position sensor
Frequency of operation	Continuous
Duration	Condition (A) and (B): 0.4 seconds Condition (C): 3 seconds Condition (D): 0.5 seconds
MIL operation	2 driving cycles
Sequence of operation	None

TYPICAL ENABLING CONDITIONS

All

The monitor will run whenever the following DTCs are not present	None
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 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 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

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	7% 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

7% 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 from 4th to 5th gear)

150 rpm or less

Vehicle speed

(After transition from 4th 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

INSPECTION PROCEDURE

PROCEDURE

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

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(d) Enter the following menus: Powertrain / 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.

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.

(d) Turn the ignition switch to ON.

(e) Turn the Techstream on.

(f) Enter the following menus: Powertrain / 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.

ECT

Tester Display

Test Part

Control Range

Diagnostic Note

Control the Shift Position

Operate shift solenoid valve and set each shift position by yourself

Press "→" button: Shift up
Press "←" button: Shift down

Possible to check operation of 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 up-shift must be performed with the accelerator pedal released.
The 5th to 4th down-shift 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.

OK:

Gear position changes in accordance with the Techstream command.

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 OFF.

HINT:

(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.

(d) Measure the line pressure with SST.

(e) Turn the Techstream on.

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

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

(h) Measure the line pressure.

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

4.	CLEAR DTC AND PERFORM RUNNING TEST

(a) Clear the DTC .

(b) Check the DTC again after conducting the Monitor Drive Pattern .

OK:

No DTC code