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: RM000000W8D03XX
Title: AB60F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: DESCRIPTION (2008 LX570)

DTC

P2757

Torque Converter Clutch Pressure Control Solenoid Performance (Shift Solenoid Valve SLU)

DESCRIPTION

The ECM uses the signals from the throttle position sensor, air-flow meter, turbine (input) speed sensor, output speed sensor and crankshaft position sensor to monitor the engagement condition of the lock-up clutch.

Then the ECM compares the engagement condition of the lock-up clutch with the lock-up schedule in the ECM memory to detect mechanical problems with shift solenoid valve SLU, the valve body and torque converter clutch.



DTC Code

DTC Detection Condition

Trouble Area

P2757

Lock-up does not occur when driving in the lock-up range (normal driving at 80 km/h (50 mph)), or lock-up remains ON in the lock-up OFF range (2 trip detection logic).
  • Shift solenoid valve SLU remains open or closed
  • Shift solenoid valve SLU
  • Valve body is blocked
  • Torque converter clutch
  • Automatic transmission (clutch, brake, gear, etc.)
  • Line pressure is too low

MONITOR DESCRIPTION

Torque converter lock-up is controlled by the ECM based on the turbine (input) speed sensor NT, output speed sensor SP2, engine speed, engine load, engine temperature, vehicle speed, transmission temperature, and gear selection. The ECM determines the lock-up status of the torque converter by comparing the engine speed (NE) to the input turbine rpm (NT). The ECM calculates the actual transmission gear by comparing input turbine rpm (NT) to output shaft rpm (SP2). When conditions are appropriate, the ECM requests lock-up by applying control voltage to shift solenoid valve SLU. When shift solenoid valve SLU is turned ON, it applies pressure to the lock-up relay valve and locks the torque converter clutch.

If the ECM detects no lock-up after lock-up has been requested or if it detects lock-up when it is not requested, the ECM interprets this as a fault in shift solenoid valve SLU or the lock-up system performance.

The ECM will illuminate the MIL and store the DTC.

Example:

When one of the following conditions is met, the system determines that there is a malfunction.

  • There is a difference in rotation between the input side (engine speed) and output side (input turbine speed) of the torque converter when the ECM commands lock-up ON.

    Engine speed is at least 70 rpm more than input turbine speed.

  • There is no difference in rotation between the input side (engine speed) and output side (input turbine speed) of the torque converter when the ECM commands lock-up OFF.

    The difference between engine speed and input turbine speed is less than 35 rpm.

MONITOR STRATEGY

Related DTCs

P2757:

Shift solenoid valve SLU/OFF malfunction

Shift solenoid valve SLU/ON malfunction

Required sensors/Components

Shift solenoid valve SLU

Frequency of operation

Continuous

Duration

OFF malfunction (A)

2 sec.

OFF malfunction (B)

0.4 sec.

ON malfunction

1.8 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

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 S3 circuit

Not circuit malfunction

Shift solenoid valve S4 circuit

Not circuit malfunction

Shift solenoid valve SR circuit

Not circuit malfunction

Shift solenoid valve SLU 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 (Engine Coolant Temperature)

40°C (104°F) or higher

Spark advance from max. retard timing by KCS control

0° crankshaft angle or more

Engine

Starting

ECM selected gear

2nd, 3rd, 4th, 5th or 6th

Vehicle speed

25 km/h (15.5 mph) or more

Shift solenoid valve S1 circuit

Not circuit off malfunction

Shift solenoid valve S3 circuit

Not circuit on malfunction

Shift solenoid valve S4 circuit

Not circuit off malfunction

Shift solenoid valve SL2 circuit

Not circuit on malfunction

1-2 shift valve

Not malfunction

Sequence valve

Not malfunction

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

OFF malfunction (A)

ECM lock-up command

ON

(SLU pressure: 513 kPa (5.2 kgf/cm2, 74 psi) or higher)

Duration time from lock-up on command

3 sec. or more

Vehicle speed

Less than 120 km/h (74.6 mph)

OFF malfunction (B)

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)

ON malfunction

ECM lock-up command

OFF

(SLU pressure: Below 4 kPa (0.04 kgf/ cm2, 0.6 psi))

Duration time from lock-up off command

3 sec. or more

Throttle valve opening angle

6% or more

Vehicle speed

Less than 120 km/h (74.6 mph) at 2nd gear

(Varies with ECM selected gear)

TYPICAL MALFUNCTION THRESHOLDS

[OFF malfunction]

When both conditions below are met: OFF malfunction (A) and (B)

OFF malfunction (A)

Engine speed - Turbine speed (NE - NT)

70 rpm or more

OFF malfunction (B)

Turbine speed/Output speed (NT/NO)

Less than 3.11 or more than 7.58

[ON malfunction]

2 detections are necessary per driving cycle:

1st detection: temporary flag ON

2nd detection: pending fault code ON

Vehicle speed must be less than 10 km/h (6.2 mph) once before 2nd detection.

Engine speed - Turbine speed (NE - NT)

Less than 35 rpm

COMPONENT OPERATING RANGE

Speed sensor (NT)

Input speed is equal to engine speed when lock-up ON.

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 engine switch off.

(c) Connect the Techstream to the DLC3.

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

(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.

Engine and ECT

Tester Display

Test Part

Control Range

Diagnostic Note

Activate the Lock Up

Control shift solenoid valve SLU to set automatic transmission to lock-up condition

ON or OFF

It is possible to check the shift solenoid valve SLU operation.

[Vehicle Condition]

  • The throttle valve opening angle is less than 35%.
  • The vehicle speed is 60 km/h (37 mph) or more.

HINT:

  • This test can be conducted when the vehicle speed is 60 km/h (37 mph) or more.
  • Perform this test while driving in 5th or 6th gear.

(h) Lightly depress the accelerator pedal and check that the engine speed does not change abruptly.



HINT:

  • When changing the accelerator pedal opening angle while driving, if the engine speed does not change abruptly, lock-up is on.
  • Slowly release the accelerator pedal in order to decelerate, but do not fully release the pedal (fully releasing the pedal will close the throttle valve and lock-up may be turned off automatically).

PROCEDURE

1.

CHECK DTC OUTPUT (IN ADDITION TO DTC P2757)

(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 P2757 is output

A

P2757 and other DTCs are output

B

HINT:

If any other codes besides P2757 are output, perform troubleshooting for those DTCs first.

A

2.

INSPECT SHIFT SOLENOID VALVE SLU

(a) Remove shift solenoid valve SLU.



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

Standard Resistance:

Tester Connection

Condition

Specified Condition

1 - 2

20°C (68°F)

5.0 to 5.6 Ω

(c) Apply battery voltage (12 V) to the shift solenoid valve and check that the valve moves and makes an operating noise.

OK:

Measurement Condition

Specified Condition
  • Battery positive (+) with a 21 W bulb → Terminal 2
  • Battery negative (-) → Terminal 1

Valve moves and makes an operating noise
OK

3.

INSPECT TRANSMISSION VALVE BODY ASSEMBLY

(a) Check the transmission valve body assembly AB60F AUTOMATIC TRANSMISSION / TRANSAXLE: VALVE BODY ASSEMBLY: DISASSEMBLY (2008 LX570) .

OK:

There are no foreign objects on any valve.

OK

4.

INSPECT TORQUE CONVERTER CLUTCH ASSEMBLY

(a) Check the torque converter clutch assembly AB60F AUTOMATIC TRANSMISSION / TRANSAXLE: TORQUE CONVERTER CLUTCH AND DRIVE PLATE: INSPECTION (2008 LX570) .

OK:

The torque converter clutch operates normally.

OK