Last Modified: 11-29-2007 1.6 C
Service Category: Drivetrain Section: Automatic Transmission/Transaxle
Model Year: 2008 Model: Sequoia Doc ID: RM000000W8003TX
Title: A750F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: DESCRIPTION (2008 Sequoia)

DTC

P0756

Shift Solenoid "B" Performance (Shift Solenoid Valve S2)

DESCRIPTION

The ECM uses signals from the output shaft speed sensor and input speed sensor to detect the actual gear position (1st, 2nd, 3rd, 4th or 5th gear).

Then the ECM compares the actual gear with the shift schedule in the ECM memory to detect mechanical problems of the shift solenoid valves, valve body or automatic transmission (clutch, brake or gear, etc.).

DTC No.

DTC Detection Condition

Trouble Area

P0756

Gear required by ECM does not match actual gear when driving. (2 trip detection logic)
  • Shift solenoid valve S2 remains open or closed
  • Shift solenoid valve SLT remains open or closed
  • Valve body is blocked
  • Automatic transmission (clutch, brake or gear, etc.)

MONITOR DESCRIPTION

This DTC indicates a stuck ON malfunction or stuck OFF malfunction of the shift solenoid valve S2.

The ECM commands gear shifts by turning the shift solenoid valves ON/OFF. When the gear position commanded by the ECM and the actual gear position are not the same, the ECM illuminates the MIL and stores the DTC.

MONITOR STRATEGY

Related DTCs

P0756:

Shift solenoid valve S2/OFF malfunction

Shift solenoid valve S2/ON malfunction

Required sensors/Components

Shift solenoid valve S2, Vehicle speed sensor, Throttle position sensor, Speed sensor (NT), Speed sensor (SP2)

Frequency of operation

Continuous

Duration

OFF malfunction (A), (B) and (C):

0.4 seconds

OFF malfunction (D):

Immediately

ON malfunction (A) and (B):

0.4 seconds

ON malfunction (C):

3 seconds

ON malfunction (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

P0115 - P0118: ECT sensor

P0125: Insufficient ECT for Closed Loop

P0500: VSS

P0748 - P0799: 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 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

Transfer Position is 4WD HIGH*

Vehicle speed sensor circuit

Not circuit malfunction

Output shaft speed sensor circuit

Not circuit malfunction

Transfer output speed

143 rpm or more

NO/NOtf (Transfer input speed/Transfer output speed)

0.9 or more, and less than 1.1

HINT:

*: This condition only applies to 4WD.

OFF Malfunction (A)

ECM selected gear

1st

Vehicle speed

2 km/h (1.2 mph) or more, and less than 40 km/h (24.9 mph)

Throttle valve opening angle

8% or more (when actual gear is 4th)

7% or more at 2000 rpm (Conditions vary with engine speed)

OFF Malfunction (B)

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)

OFF Malfunction (C)

Current ECM selected gear

5th

Last ECM selected gear

4th

Continuous time for ECM selecting 4th gear

2 seconds or more

Actual gear when ECM selected 4th gear

4th

OFF Malfunction (D)

Current ECM selected gear

5th

Last ECM selected gear

4th

ON Malfunction (A)

ECM selected gear

1st

Vehicle speed

2 km/h (1.2 mph) or more, and less than 40 km/h (24.9 mph)

Throttle valve opening angle

8% or more (when actual gear is 4th)

7% or more at 2000 rpm (Conditions vary with engine speed)

ON Malfunction (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)

ON Malfunction (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)

ON Malfunction (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

[OFF malfunction]

All of the following are met: OFF malfunction (A), (B), (C) and (D)

2 detections are necessary per driving cycle:

1st detection: Temporary flag ON

2nd detection: Pending fault code ON

OFF Malfunction (A) and (B)

Turbine speed/Output speed (NT/NO)

3.30 or more, and 7.50 or less

(This means actual gear is 1st)

OFF Malfunction (C)

Turbine speed/Output speed (NT/NO)

0.65 or more, and 0.79 or less

(This means actual gear is 5th)

OFF Malfunction (D)

Output record of ECU from 4th to 5th up-shifting

Recorded

[ON malfunction]

Both of the following conditions are met:

ON malfunction (A) or (B), and ON malfunction (C) or (D)

ON Malfunction (A)

Turbine speed/Output speed (NT/NO)

1.91 or more, and 2.35 or less

(This means actual gear is 2nd)

ON Malfunction (B)

Turbine speed/Output speed (NT/NO)

1.28 or more, and 1.53 or less

(This means actual gear is 3rd)

ON Malfunction (C)

Turbine speed - Output speed x 4th gear ratio

(NT - NO x 4th gear ratio)

1000 rpm or more

ON Malfunction (D)

Turbine speed - Output speed x 5th gear ratio

(NT - NO x 5th gear ratio)

1000 rpm or more

INSPECTION PROCEDURE

1. ACTIVE 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 / 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.

Comparing the shift position commanded by the Active Test with the actual shift position enables you to confirm the problem A750F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: FAIL-SAFE CHART (2008 Sequoia) .

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.
  • The shift solenoid valve S2 turns ON/OFF normally when the shift lever is in D.

    ECM gear shift command

    1st

    2nd

    3rd

    4th

    5th

    Shift solenoid valve S2

    OFF

    ON

    ON

    OFF

    OFF

PROCEDURE

1.

CHECK DTC OUTPUT (IN ADDITION TO DTC P0756)

(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 / ECT / Trouble Codes.

(e) Read the DTCs using the Techstream.

Result

Result

Proceed to

Only P0756 is output

A

P0756 and other DTCs are output

B

HINT:

If any other codes besides P0756 are output, perform troubleshooting for those DTCs first.

A

2.

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:

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 / 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 A750F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: HYDRAULIC TEST (2008 Sequoia) 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.

OK

3.

INSPECT SHIFT SOLENOID VALVE S2

(a) Remove the shift solenoid valve S2.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

Shift solenoid valve S2 connector terminal - Shift solenoid valve S2 body

20°C (68°F)

11 to 15 Ω

(c) Connect the battery positive (+) lead to the terminal of the solenoid valve connector, and the negative (-) lead to the solenoid valve body. Then check that the valve moves and makes an operating noise.

OK:

Valve moves and makes an operating noise.

OK

4.

INSPECT TRANSMISSION VALVE BODY ASSEMBLY

(a) Check the transmission valve body assembly.

OK:

There are no foreign objects on each valve.

OK