Transfer (UF1AE): Other Lexus IS II

PRECAUTION

Note. When disconnecting the negative (-) battery cable, initialize the following systems after the cable is reconnected.

INITIALIZE SYSTEM REFERENCE

1. The automatic transmission with transfer is composed of highly precision-finished parts. Inspect all parts carefully before reassembly. Even a small nick could cause fluid leakage or affect the performance of the transfer system.
2. All disassembled parts should be washed clean. All fluid passages and holes should be blown through with compressed air.
3. Dry all parts with compressed air only. Never use a shop rag or piece of cloth to dry them.
4. Only recommended automatic transmission fluid or kerosene should be used for cleaning.
5. After cleaning, the parts should be arranged in their correct order for efficient inspection, repairs, and reassembly.
6. All replacement discs for the clutch must be soaked in ATF for at least 15 minutes before reassembly.
7. All seal rings, clutch discs, clutch plates, rotating parts, and sliding surfaces should be coated with ATF prior to reassembly.
8. All rubber O-rings should be replaced.
9. Make sure that the ends of a snap ring are not aligned with one of the cutouts and are installed in the groove correctly.
10. Check bearings for wear or damage. Replace them as necessary.
11. When working with FIPG material, you must observe the following: Use a razor blade and a gasket scraper to remove all the old packing (FIPG) material from the gasket surface. Clean all components thoroughly to remove any loose material. Clean both sealing surfaces with a non-residue solvent. Reassemble the parts within 5 minutes of applying fresh FIPG material. Otherwise, the packing (FIPG) material must be removed and reapplied. Do not fill the reservoir with ATF immediately after reassembling the parts. Wait at least 1 hour before adding ATF.
12. When there is a malfunction in the contact point of the terminals or installation problems with parts, removal and installation of the suspected problem parts may return the system to the normal condition either completely or temporarily.
13. In order to determine the malfunctioning area, be sure to check the conditions at the time the malfunction occurred, such as by DTC output and record it before disconnecting each connector or removing and installing parts.
14. Since the Four Wheel Drive Control System (4WD Control System) may be influenced by a malfunction in other systems, be sure to check for DTCs in the other systems.
15. When removing and installing the 4WD control ECU and each sensor, be sure to check that the normal display is output in Test Mode inspection and in DTC output inspection after installing all the parts.
16. The CAN communication system is used for data communication between each of the ECUs and sensors. If there is trouble in the CAN communication line, the DTC of the communication line is output.
17. If the DTC of the CAN communication line is output, repair the malfunction in the communication line and troubleshoot the 4WD Control System.
18. Since the CAN communication line has its own length and route, it cannot be repaired temporarily with the bypass wire, etc.

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COMMUNICATION REFERENCE

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1. GENERAL DESCRIPTION The Four Wheel Drive Control System (4WD Control System) consists of the hydraulic control mechanism of the transfer unit, steering angle sensor, wheel speed sensor, skid control ECU, and 4WD control ECU. The 4WD Control ECU controls the fluid pressure in the center differential limiting clutch to distribute the drive force to the front and rear wheels in accordance with the vehicle speed and vehicle behavior. Thus, it helps create a stable driving performance. Main components and their functions. COMPONENTS FUNCTION Component Function 4WD Warning (Multi-information Display) Displays a warning to the driver when the system malfunctions Slip Indicator Light Notifies driver that the current road surface is slippery Stop Light Switch Detects the brake operation Throttle Position Sensor Detects the opening angle of the throttle valve Park/Neutral Position Switch Detects the "P/N" position Steering Angle Sensor Detects turning of the steering wheel Linear Solenoid (Transfer control solenoid) Controls hydraulic pressure of the center differential control limiting clutch in accordance with the signals from the 4WD control ECU Brake Actuator assembly (Skid Control ECU) Detects the signals from each sensor and outputs them to the 4WD control ECU 4WD Control ECU Detects the signals provided by various sensors via the skid control ECU, actuates the linear solenoid, and controls the system ECM Sends the throttle valve angle signal and park / neutral position switch signal to the skid control ECU Speed Sensor Detects the wheel speed of each 4 wheels
2. FOUR WHEEL DRIVE CONTROL SYSTEM OUTLINE The four wheel drive control system (4WD control system) is a full-time 4WD system that electronically controls the center differential limiting clutch of the transfer to distribute optimal drive forces to the front and rear wheels in accordance with the driving conditions. This system adopts a UF1A transfer case that uses a planetary gear type center differential in the transfer section. A wet type multiple disc clutch in the differential control limiting clutch and a silent chain are used to transfer driving force to the front wheels. Four wheel drive control system function. OPERATION AND DESCRIPTION Operation Description Vehicle initial acceleration and low-speed turn control This controls the amount of sideway sliding that occurs at the rear of vehicles when accelerating from a stop to improve acceleration and hill climbing capacity This prevents tight corner braking during a low-speed turn Slip control at vehicle initial acceleration This helps prevent the vehicle from sliding sideways, when accelerating from a stop with the steering wheel turned and ensures a stable start up and steerability Slip control This ensures high turning performance and stability not affected by road surface conditions during mid and high speed running Acceleration control This controls straight-line running when accelerating during mid and high speed running to ensure straight-line capacity and stability of the vehicle
3. SYSTEM OPERATION Vehicle Start up and Low-speed Turn Control The 4WD control ECU controls the transfer control solenoid based on signals from the throttle position sensor and steering angle sensor. The transfer control solenoid controls the fluid pressure applied to the center differential limiting clutch. Thus, vehicle start up and low-speed turn control will be performed. The 4WD control ECU controls the center differential coupling it directly before starting the vehicle in order to prevent slipping at vehicle initial acceleration or during acceleration on a grade or a low friction road. The 4WD control ECU decreases the fluid pressure applied to the center differential limiting clutch during a low-speed turn based on the steering angle to prevent tight corner braking. Slip Control at Vehicle Start up The 4WD control ECU controls the transfer control solenoid based on signals from the throttle position sensor and speed sensor. The transfer control solenoid controls the fluid pressure applied to the center differential limiting clutch. Thus, slip control at vehicle initial acceleration will be performed. If the vehicle starts moving with the steering wheel turned, the fluid pressure applied to the center differential limiting clutch is decreased by low-speed turn control. An excessive driving force may be applied to the rear wheels on a low friction road, causing the vehicle rear to move sideways. To prevent this, the 4WD control ECU detects differences between the front wheel speed and the rear wheel speed based on signals from the speed sensors to directly couple the center differential immediately. Slip Control The 4WD control ECU controls the transfer control solenoid based on signals from the speed sensor. The transfer control solenoid controls the fluid pressure applied to the center differential limiting clutch. Thus, slip control will be performed. The 4WD control ECU detects differences between the front wheel speed and the rear wheel speed while driving at a medium or high speed based on signals from the speed sensors. Then, the 4WD control ECU calculates the fluid pressure required based on the difference in the wheel speeds and the vehicle speed and continuously applies the appropriate fluid pressure to the center differential limiting clutch, which stabilizes the vehicle. Acceleration Control The 4WD control ECU controls the transfer control solenoid based on the throttle position sensor and speed sensors. The transfer control solenoid controls the fluid pressure applied to the center differential limiting clutch. Thus, acceleration control will be performed. If the difference between the front wheel speed and the rear wheel speed exceeds the specified value while driving at a medium or high speed, the 4WD control ECU, in accordance with the throttle valve angle, increases the fluid pressure applied to the center differential limiting clutch to directly couple the center differential. This prevents the rear wheels from slipping and stabilizes the vehicle.
4. MECHANISM REFERENCE Mechanism of the Center Differential. The center differential distributes the power from the transmission to the front and rear wheels. In addition, it absorbs the rotational difference between the front and rear drive shafts that is created during cornering. A planetary gear is used for the center differential, which unevenly distributes the driving force to the front and rear wheels. The center differential receives the drive force that is input by the transmission by way of the planetary carrier. The planetary carrier and the sun gear are controlled by the differential limiting clutch until they are in the lockup state. A compact, lightweight and extremely silent chain is used for the front wheel drive transmission, and the driving force is transferred to the front wheel drive shaft by the sun gear of the center differential. The drive force to the rear wheel drive shaft is output in a straight line with the transmission. Mechanism of the Center Differential Control Limiting Clutch. The center differential control limiting clutch is located between the planetary gear and the front wheel driving force distribution section. It consists of wet type clutch discs, plates, and piston. Its basic structure is the same as the clutch of an automatic transmission. This clutch utilizes the friction resistance, which is created by the speed difference that occurs between the plates and discs, to transmit torque and distribute torque to the center differential limiting clutch and the front and rear wheels. Adjustment of differential control limiting force is controlled by changing the hydraulic pressure that functions in the piston. Mechanism of the Hydraulic Control (ATF Pressure Control). Line pressure for transmission control is also used by the transfer to simplify the transfer hydraulic system. Line pressure from the transmission is controlled by a modulator valve so that it does not rise above a specific pressure. This stabilizes hydraulic control of the linear solenoid valve. Hydraulic pressure controlled by the linear solenoid valve operates the control valve. It also controls the slip status of the center differential control limiting clutch by modulating the line hydraulic pressure from the transmission in the linear solenoid (transfer control solenoid). Mechanism of the Valve body & Linear Solenoid (Transfer Control Solenoid). The valve body, which is located in the bottom of the transfer case, has a two-stage composition consisting of an upper valve body and a valve body cover. The transfer control solenoid is installed in the upper valve body. The linear solenoid is integrated with electromagnetic section and the pressure modulating section. The spool pushes the pressure modulator valve according to the electric current value that makes the electromagnetic section function. The pressure modulating valve then generates hydraulic pressure to resist the pushing force of the spool, so it is possible to obtain hydraulic pressure proportional to the electric current value.

TERMINALS OF ECU

HINT

Inspect the connector from the back side while the connector is connected.

1. 4WD CONTROL ECU

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TERMINALS SPECIFIED CONDITIONS

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1. Waveform 1 (Reference): WAVEFORM 1 (REFERENCE) Item Contents Tool setting 2 V/DIV, 2 ms./DIV Vehicle condition Driving at approximately 18 mph (30 km/h) HINT: As vehicle speed (wheel rotation speed) increases, the width of the waveform narrows.
2. Waveform 2 (Reference)

WAVEFORM 2 (REFERENCE)

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1. DIAGNOSIS SYSTEM Inspect the battery voltage. Standard voltage: 11 to 14 V If the voltage is below 11 V, recharge the battery before proceeding. Check the DLC3. The 4WD control ECU uses CAN and the ISO 9141- 2 for communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 9141-2 format. Verify the conditions listed in «TERMINALS SPECIFIED CONDITIONS TABLE»(ref-235567-S23549959962006062400000). TERMINALS SPECIFIED CONDITIONS TABLE Symbols (Terminal No.) Terminal Description Condition Specified condition SIL (7) - SG (5) Bus "+" line During transmission Pulse generation CG (4) - Body ground Chassis ground Always Below 1 ohms SG (5) - Body ground Signal ground Always Below 1 ohms BAT (16) - Body ground Battery positive Always 11 to 14 V CANH (6) - CANL (14) HIGH-level CAN bus line Engine switch off 54 to 67 ohms CANH (6) - Battery positive HIGH-level CAN bus line Engine switch off 1 M ohms or higher CANH (6) - CG (4) HIGH-level CAN bus line Engine switch off 3 k ohms or higher CANL (14) - Battery positive LOW-level CAN bus line Engine switch off 1 M ohms or higher CANL (14) - CG (4) LOW-level CAN bus line Engine switch off 3 k ohms or higher HINT: If the display shows a communication error message when the cable of the intelligent tester is connected to the DLC3, the engine switch is turned on (IG) and the intelligent tester is operated, there is a problem on either the vehicle side or the tester side. If communication is normal when the tool is connected to another vehicle, inspect the DLC3 on the original vehicle. If communication is still not possible when the tester is connected to another vehicle, the problem is probably in the tester itself. Consult the Service Department listed in the tester's operator's manual.
2. FUNCTION OF 4WD INDICATOR The 4WD indicator light in the combination meter assembly (multi-information display) warns the driver of abnormal or poor condition of the four wheel drive control system.
3. CHECK 4WD INDICATOR LIGHT Using SST, connect terminals TC and CG of the DLC3 (to enter the DTC output mode). SST 09843-18040 Turn the engine switch on (IG). "DIAG" is displayed on the multi-information display, and the 4WD control ECU checks the system for malfunctions. If the 4WD control system is normal, "DIAG 4WD OK" will be displayed on the multi-information display. If the 4WD control system is not normal, "DIAG 4WD XX (DTC)" will be displayed on the multi-information display. Although the Test Mode is not set for the 4WD control system, the message (Scheme 187)will be displayed on the multi-information display when the Test Mode is activated to check the VSC, etc. HINT: Test Mode DTCs will not be stored because the Test Mode is not set. On the multi-information display, VSC, TIRE PRESSURE and 4WD are displayed in order. If the systems above are not displayed on the multi-information display, there may be a malfunction in «TC and CG Terminal Circuit»(ref-235567-S11056419792006062400000). If the 4WD indicator light check result is not normal, proceed to troubleshooting for the 4WD indicator light circuit. TROUBLESHOOTING REFERENCE Trouble Area See procedure 4WD indicator light (Remains on) «PROBLEM SYMPTOMS TABLE»(ref-235567-S21957095582006062400000) 4WD indicator light (Does not come on)
4. FAIL-SAFE FUNCTION

1. If following malfunctions occur, the 4WD control ECU will stop the function of 4WD control system or partly change the function to control the system.

MALFUNCTION REFERENCE

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1. DTC CHECK (INTELLIGENT TESTER) Check the DTCs. Connect the intelligent tester to the DLC3. Turn the engine switch on (IG). Check the DTCs by following the prompts on the tester screen. HINT: Refer to the intelligent tester operator's manual for further details. Clear the DTCs. Connect the intelligent tester to the DLC3. Turn the engine switch on (IG). Clear the DTCs by following the prompts on the tester screen. HINT: Refer to the intelligent tester operator's manual for further details.
2. DTC CHECK (SST CHECK WIRE)

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1. Check the DTCs. Using the SST, connect terminals TC and CG of the DLC3 (enter in the DTC output mode). SST 09843-18040 Turn the engine switch on (IG). "DIAG" is displayed on the multi-information display, and the 4WD control ECU checks the system for malfunctions. If the 4WD control system is normal, "DIAG 4WD OK" will be displayed on the multi-information display (normal system code). If the 4WD control system is not normal, "DIAG 4WD XX (DTC)" will be displayed on the multi-information display.
2. Clear the DTCs. Using SST, connect terminals TC and CG of the DLC3. SST 09843-18040 Turn the engine switch on (IG). Clear the DTCs stored in the 4WD control ECU by depressing the brake pedal 8 times or more within 5 seconds. Check that the 4WD indicator light (multi-information display) indicated a "4WD OK". Turn the engine switch off. Remove the SST from the terminals of DLC3.