Construction
The trochoid pump is housed in the oil pump housing. It consists of a inner rotor (9 teeth), outer rotor (10 teeth) and oil pump cover.
Identifying Oil Pump Components. Scheme 1192
Scheme 1193
- The automatic transmission fluid (ATF) is drawn through the oil strainer mounted under the control valve ASSEMBLY, and is routed to the transmission case, to the oil pump housing, and to the oil pump cover. It then goes to the suction port.
- As the inner rotor rotates, the outer rotor also rotates. This motion causes ATF to be sucked up through the suction port and discharged under pressure from the discharged port.
- The discharged ATF flows from the oil pump cover to the oil pump housing. It then goes to the transmission case, the control valve and to the regulator valve, thus serving as hydraulic oil and lubricating oil for the torque converter clutch, valves, clutch.
- As engine speed increases, the delivery rate of the trochoid pump also increases. (Scheme 1193): Oil Pump Schematic
Identifying Reverse Clutch Components. Scheme 1194
HIGH CLUTCH
In 3rd and 4th speed operation, hydraulic pressure is applied to the high clutch from the control valve and another hydraulic pressure controller. The clutch plates (drive and driven plates) are connected by this hydraulic pressure, and engine power from the input shaft is transmitted to the front planetary carrier through the high clutch hub.
A cover is placed inside the piston, and the space between the high clutch piston and the cover is filled with ATF. The centrifugal force of this ATF, when the high clutch is not in engagement, acts to cancel the centrifugal force generated by ATF remaining in the oil chamber in the high clutch piston, which otherwise is likely to push the piston, preventing the clutch from being disengaged completely.
When the high clutch is in operation, the piston is not pushed back because a large hydraulic pressure is being applied on it, thereby the high clutch being kept engaged.
Identifying High Clutch Components. Scheme 1195
The 2-4 brake is composed of a 2-4 brake piston, spring retainer, pressure plate, drive plates and driven plates.
This clutch operates with hydraulic pressure from the transmission control valve to fix the front sun gear when the 2nd gear is selected in D, 3 or 2 range, or when the 4th gear is selected in D range.
Identifying 2-4 Brake Components. Scheme 1196
The piston, dish plate, drive plate, driven plate, retaining plate and snap ring are mounted directly to the transmission case. The spring retainer which is integral with the spring is secured to the inner race of the transmission case engagement surface.
Identifying Low & Reverse Brake Components. Scheme 1197
During 1st speed of the "1st", and reverse, hydraulic pressure from the hydraulic pressure controller is applied to the low & reverse piston. This pressure causes the drive plate and driven plate to engage, and the low clutch to be fixed.
The low clutch consists of a clutch drum, clutch piston, return spring, cover, drive plates, driven plates etc.
The low clutch drum is manufactured by pressing sheet metal. The clutch drum, outer race and sleeve are welded together by the electron beam welding technique.
Identifying Low Clutch Components. Scheme 1198
The low clutch operates in "D" (1st, 2nd, 3rd speed), "3" (1st, 2nd, 3rd speed), "2" and "1" ranges. This clutch engages when the hydraulic pressure from the transmission control valve is applied to the low clutch piston, transmitting the power to the reduction drive shaft.
A cover is placed inside the piston, and the space between the low clutch piston and the cover is filled with ATF. The centrifugal force of this ATF, when the low clutch is not in engagement, acts to cancel the centrifugal force generated by ATF remaining in the oil chamber in the low clutch piston, which otherwise is likely to push the piston, preventing the clutch from being disengaged completely.
When the low clutch is in operation, the piston is not pushed back because a large hydraulic pressure is being applied on it, thereby the low clutch being kept engaged.
Low Clutch - Function. Scheme 1199
HYDRAULIC CONTROL VALVE
The hydraulic control system consists of an oil pump, control valve bodies, clutches and connecting passages and pipes. When it is activated manually, or automatically by the electronic control system, it hydraulically controls the gear shifting mechanism.
Identifying Hydraulic Control Valve Components. Scheme 1200
Hydraulic Control Valve Function Chart (1 Of 2). Scheme 1201
Hydraulic Control Valve Function Chart (2 Of 2). Scheme 1202
The gear train consists of two sets of planetary gears, three sets of multi-plate clutches, two sets of multi-plate brakes and one set of one-way clutch.
Identifying Power Train Components. Scheme 1203
Power Train Operation Table. Scheme 1204
N Range
Since the rear sun gear and the high clutch drum are in mesh with the input shaft, they rotate together with input shaft.
The high clutch drum does not transmit the rotation torque to the planetary unit since the reverse clutch and the high clutch are in the free state.
The rotation torque of the rear sun gear is transmitted to the rear internal gear through the pinion gear.
However, the rotation torque of the rear sun gear is not transmitted to the rear planetary carrier since the rear internal gear idles because of disengaged low clutch.
Accordingly, the rotation torque of the input shaft is not transmitted to the reduction drive shaft.
N Range - Operation (1 Of 2). Scheme 1205
N Range - Operation (2 Of 2). Scheme 1206
P Range
All controls do not operate, just as in the N range. The parking pawl locks the power train by pawling the parking gear which is integrated with the reduction drive gear.
P Range - Operation (1 Of 2). Scheme 1207
P Range - Operation (2 Of 2). Scheme 1208
First Speed Of D Or 3 Range (D 1 , 3 1 )
At 1st speed of these ranges, only the low clutch is in engagement. The rear internal gear which rotates idly in P and N ranges tries to rotate counterclockwise due to engaged low clutch. However, this is blocked by the one-way clutch and secured to the transmission case.
Therefore, the rotation of the rear sun gear is converted to the revolution of the pinion gears around the sun gear, causing the planetary carrier to rotate. In this way, the rotation of the input shaft is transmitted to the reduction drive shaft after subjected to speed reduction by the planetary gear. On the other hand, the rear internal gear rotates clockwise if the reverse driving force is applied from the reduction drive shaft during coasting. This rotation frees the one-way clutch. Accordingly, since the connection between the reduction drive shaft and the input shaft is lost, the engine braking effect is not available.
Scheme 1209
Scheme 1210
Second Speed Of D, 3 Or 2 Range (D 2 , 3 2 , 2 2 )
At 2nd speed, the 2-4 brake as well as the low clutch is in engagement. In addition to the elements operating at 1st speed, the front sun gear which idles at 1st speed is connected to the transmission case because of engaged 2-4 brake. In this state, the rotation torque of the rear sun gear is transmitted to the rear internal gear through the front internal gear, front pinion gears, low clutch drum and low clutch. At this time, the one-way clutch is free since the low clutch drum rotates clockwise. For this reason, the rotation speed is higher than that at 1st gear by an amount of rear internal gear rotation speed.
At 2nd speed, the driving power is transmitted without being affected by the one-way clutch. Therefore, the back driving force from the reduction drive shaft is transmitted to the input shaft, thus the engine braking effect being available.
Scheme 1211
Scheme 1212
Third Speed Of D Or 3 Range (D 3 , 3 3 )
At 3rd speed, the low clutch and the high clutch are thrown into engagement. With the high clutch engaged, the high clutch drum rotates, which is turn rotates the rear internal gear through the front planetary carrier, low clutch drum and low clutch. This means that the rear sun gear and the rear internal gear rotates at the same speed. That is, the rear pinion gears stop rotation on its axis and resolve around the sun gear as a planetary assembly.
As a result, the input shaft and the reduction drive shaft rotate at the same speed.
The one-way clutch is released because the low clutch rotates clockwise. Since the driving power is transmitted without being affected by the one-way clutch, the back driving force from the reduction drive shaft is transmitted to the input shaft, thus the engine braking effect being available.
Scheme 1213
Scheme 1214
Fourth Speed Of D Range (D 4 )
At 4th speed, the high clutch and the 2-4 brake are thrown into engagement. The engaged high clutch causes the front planetary carrier to rotate. The engaged 2-4 brake causes the front sun gear which idles at 3rd speed to be locked.
The front planetary carrier rotates at the same speed as the input shaft. The rotation of the front planetary carrier causes the front pinion gears to revolve around the stationary front sun gear, which causes the front internal gear to rotate faster than the input shaft.
As a result, the reduction drive shaft is driven at a higher speed than the input shaft.
The one-way clutch is free because the low clutch rotates clockwise. Since the driving power is transmitted without being affected by the one-way clutch, the back driving force from the reduction drive shaft is transmitted to the input shaft, thus the engine braking effect being available.
Scheme 1215
Scheme 1216
First Speed Of 1 Range
At 1st speed of this range, the low clutch and the low & reverse brake are thrown into engagement. The 1st speed in this range shows the same operation as the 1st speed in the D or 3 range. However, the one-way clutch produces no effect because the low & reverse brake is operated.
The rear internal gear is always interlocked with the transmission case by the engaged low & reverse brake.
During coasting, therefore, the back driving force from the reduction drive gear is transmitted to the input shaft. This means, unlike the 1st speed in D or 3 range, that the engine braking effect is available in this range.
First Speed Of 1 Range - Operation (1 Of 2). Scheme 1217
First Speed Of 1 Range - Operation (2 Of 2). Scheme 1218
R Range
In "R" range, the reverse clutch and the low & reverse brake are thrown into engagement. The engaged reverse clutch allows the front sun gear to rotate, while the engaged low & reverse brake allows the low clutch drum to be interlocked with the transmission case.
The rotation of the input shaft causes the front sun gear to rotate, which in turn causes the front pinion gears to rotate in the reverse direction. Thus, the rotation torque of the input shaft is transmitted to the front internal gear.
At this time, the rotation speed transmitted to the front internal gear is reduced by the front sun gear and the front pinion gears.
The one-way clutch produces no effect because the low & reverse brake is in engagement.
In this range, since the power transmission is made without influence of the one-way clutch, the back driving force from the reduction drive shaft is transmitted to the input shaft, thus the braking effect of the engine being available.
R Range - Operation (1 Of 2). Scheme 1219
R Range - Operation (2 Of 2). Scheme 1220
P & N Range - Schematic Drawing (1 Of 2). Scheme 1221
P & N Range - Schematic Drawing (2 Of 2). Scheme 1222
R Range - Schematic Drawing (1 Of 2). Scheme 1223
R Range - Schematic Drawing (2 Of 2). Scheme 1224
Fourth Speed Of D Range (Lock-Up Off) - Schematic Drawing (1 Of 2). Scheme 1225
Fourth Speed Of D Range (Lock-Up Off) - Schematic Drawing (2 Of 2). Scheme 1226
Fourth Speed Of D Range (Lock-Up On) - Schematic Drawing (1 Of 2). Scheme 1227
Fourth Speed Of D Range (Lock-Up On) - Schematic Drawing (2 Of 2). Scheme 1228
Third Speed Of D & 3 Range - Schematic Drawing (1 Of 2). Scheme 1229
Third Speed Of D & 3 Range - Schematic Drawing (2 Of 2). Scheme 1230
Second Speed Of D, 3 & 2 Range - Schematic Drawing (1 Of 2). Scheme 1231
Second Speed Of D, 3 & 2 Range - Schematic Drawing (2 Of 2). Scheme 1232
First Speed Of D, 3 & 2 Range - Schematic Drawing (1 Of 2). Scheme 1233
First Speed Of D, 3 & 2 Range - Schematic Drawing (2 Of 2). Scheme 1234
First Speed Of 1 Range - Schematic Drawing (1 Of 2). Scheme 1235
First Speed Of 1 Range - Schematic Drawing (2 Of 2). Scheme 1236
Outline
This is the electronically controlled MP-T (multi-plate transfer) type AWD transfer system, originally designed for SUBARU, consisting of a transfer hydraulic pressure control unit incorporating a vehicle speed sensor, control unit, and duty solenoid and a transfer clutch (hydraulic multi-plate clutch).
The control unit stores optimum transfer clutch torque data for a variety of driving conditions. When actual driving conditions (vehicle speed, throttle opening, gear range, wheel slip, etc.) are detected by various sensors, the control unit selects a duty ratio most suitable to the given condition from the memory. It then controls the operation of the transfer clutch by means of the hydraulic pressure which controls the duty solenoid and provides optimum rear torque distribution.
Various sensors and the control unit also serve as gear shift control, lock-up control and hydraulic pressure control.
Identifying AWD Transfer System Components. Scheme 1237
Transfer Clutch (Multi-Plate Clutch)
The transfer unit consists of a hydraulic multi-plate clutch and a transfer hydraulic control system incorporating a transfer duty solenoid, rear drive shaft, etc.
The transmission control unit has duty ratios memorized in advance according to running conditions. In order to obtain the optimum transfer torque for the running condition, the oil pressure that is applied to the drive plates and driven plates is controlled by applying oil pressure to the transfer piston from the transfer oil pressure control device including the duty solenoid.
Also, the transfer clutch drum and rear drive shaft are joined to each other by welding. The rear drive shaft has drilled oil passages for transfer clutch control and also for lubrication of extension bushing and ball bearing in it.
Identifying Transfer Clutch (Multi-Plate Clutch) Components. Scheme 1238
Transfer Oil Pressure Control Device
The transfer control valve body is bolted the rear end of transmission case through transfer valve plate.
Hydraulic pressure used in the transfer valve body (line pressure and pilot pressure) are supplied from the transmission control valve body through the transmission case.
The transfer duty solenoid modulates the pilot pressure into the transfer duty pressure depending on the signals from transmission control module (TCM).
The transfer duty pressure in turn modulates the line pressure into the transfer clutch pressure before it is sent to the transfer control valve.
The transfer clutch pressure puts the transfer clutch into engagement depending on the driving conditions so that the optimum torque may be distributed to the rear wheels.
Identifying Transfer Oil Pressure Control Device. Scheme 1239
General
The electronic-hydraulic control system consists of various sensors and switches, a transmission control module (TCM) and the hydraulic controller including solenoid valves. The system controls the transmission proper including shift control, lock-up control, timing control, reverse inhibit control, engine control, line pressure control, auto pattern select control and shift timing control. It also controls the AWD transfer clutch. In other words, the system detects various operating conditions from various input signals and sends output signals to shift solenoids 1 and 2, low clutch timing solenoid, 2-4 brake timing solenoid, line pressure, lock-up, transfer and 2-4 brake duty solenoids (a total of eight solenoids).
Identifying Electronic-Hydraulic Control System. Scheme 1240
Input Signal Chart. Scheme 1241
Output Signal Chart. Scheme 1242
Control Item Chart. Scheme 1243
Throttle Position Sensor
The throttle position sensor provides electrical signals corresponding to the throttle position. The throttle position and accelerator depression speed are detected by this throttle position sensor output.
Vehicle Speed Sensor 1 (Rear)
The vehicle speed sensor 1 (output shaft rotation sensor) is mounted to the extension case (from the outside of the case). It detects the rear wheel speed based on the peripheral speed of the transfer clutch drum and sends sine wave signals (30 pulses per rotation) to TCM.
Identifying Vehicle Speed Sensor 1 (Rear). Scheme 1244
Vehicle Speed Sensor 2 (Front)
The vehicle speed sensor 2 (output shaft rotation sensor) is mounted to the transmission case (from the outside of the case). It detects the front wheel speed and sends sine wave signals (16 pulses per rotation) to TCM.
The TCM converts the signals into 4-pulse normal wave signals and outputs them to the engine control module (ECM) and the combination meter.
Identifying Vehicle Speed Sensor 2 (Front). Scheme 1245
ATF Temperature Sensor
This sensor is mounted to the control valve in the transmission. It detects temperature change as an analog electrical signal. The output characteristics of the sensor are shown below.
Identifying ATF Temperature Sensor. Scheme 1246
Inhibitor Switch
The inhibitor switch assures safety when starting the engine. This switch is mounted on the right side of the transmission case, and is operated by the range selector lever.
When the selector lever is set to "P" or "N", the electrical circuit is connected in the inhibitor switch and the starter circuit is energized for cranking the engine.
When the selector lever is set to "R", "D", "3", "2", or "1" range, the electrical circuit is disconnected in the inhibitor switch. Hence engine cranking is disabled. In the "R" range, the backup light circuit is completed in the switch, and the backup lights come on.
In addition to the above function, the inhibitor switch incorporates a circuit for detecting the selected range position and sending the range signal to the TCM.
Identifying Inhibitor Switch. Scheme 1247
Shift Solenoid 1 & 2
These solenoids are mounted to the control valve. They are turned ON or OFF according to signals sent from the TCM. The gear positions are changed according to the ON and OFF condition of these solenoids.
Identifying Shift Solenoid 1 & 2. Scheme 1248
Low Clutch Timing Solenoid
This solenoid is mounted to the control valve, and it is turned ON or OFF according to the signal sent from the TCM. It then controls the low clutch timing valve B and reverse inhibit valve.
Identifying Low Clutch Timing Solenoid. Scheme 1249
2-4 Brake Timing Solenoid
This solenoid is mounted to the control valve, and it is turned ON or OFF according to the signal sent from the TCM. It then controls the 2-4 brake timing valve B for decreasing the change gear shock.
Identifying 2-4 Brake Timing Solenoid. Scheme 1250
This solenoid is mounted to the control valve, and its duty ratio is controlled by the signal sent from TCM. This solenoid then controls the pressure modifier valve and accumulator control valve A to adjust the line pressure to an optimum pressure level suitable for operating conditions.
Identifying 2-4 Brake Timing Solenoid. Scheme 1251
Lock-Up Duty Solenoid
This solenoid is mounted to the control valve, and its duty ratio is controlled by the signal sent from TCM. It then controls the lock-up control valve to provide smooth engagement and disengagement of the lock-up clutch.
Identifying Lock-Up Duty Solenoid. Scheme 1252
Brake Duty Solenoid
This solenoid is mounted to the control valve, and its duty ratio is controlled by the signal sent from TCM. It modulates the 2-4 brake duty pressure when the 2-4 brake is operated, reducing shifting shocks.
Identifying Brake Duty Solenoid. Scheme 1253
Transfer Duty Solenoid
This solenoid is mounted to the transfer control valve on the rear end of transmission case, and its duty ratio is controlled by the signal sent from TCM. It then controls the transfer control valve for controlling the transfer clutch hydraulic oil pressure.
Identifying Transfer Duty Solenoid. Scheme 1254
TRANSMISSION CONTROL MODULE (TCM)
TCM receives various sensor signals and determines the running conditions of the vehicle. It then sends control signals to each solenoid according to the preset gearshift characteristic data, lockup operation data, and transfer clutch torque data (duty ratio).
Control System Chart (1 Of 2). Scheme 1255
Control System Chart (2 Of 2). Scheme 1256
TCM System Diagram. Scheme 1257
Shift Control
Gear shifting is controlled in response to driving conditions, according to the shift point characteristic data stored in the TCM. Solenoids are operated at the proper time corresponding to the shift pattern, throttle position, and vehicle speed for smooth shifting.
Note. When oil temperature is below approximately 10°C (50°F), the vehicle cannot be shifted to the 4th gear.
Shift Control (1 Of 3). Scheme 1258
Shift Control (2 Of 3). Scheme 1259
Scheme 1260
- Control module activates both solenoids 1 and 2 in response to throttle and vehicle speed signals.
- Shift valve moves in response to solenoid operation, supplying/interrupting clutch pressure to the line.
- Gears are shifted by ON-OFF operation of both solenoids as indicated in table. (Scheme 1260): Shift Control (3 Of 3)
Lock-Up Control
The lock-up engaging and disengaging conditions are set for each gear shift range, gear position and shift pattern and correspond to the throttle position and vehicle speed, and the duty solenoid electronically controlled by TCM controls the lock-up clutch. The lock-up clutch engagement and disengagement are controlled by the lock-up control valve.
< When engaging and disengaging >
The lock-up control valve engages and disengages the lock-up clutch by adjusting the hydraulic pressure.
Electronic Control Of Clutch Oil Pressure In Summary
- Solenoids activate through the TCM which receives various control signals (throttle signal, etc.)
- Control signals are converted into line pressure duty pressure, which is transmitted to the pressure modifier valve.
Shift Pattern Select Control
Shift pattern is selectable automatically between a base pattern suitable for ordinary economy running and a power pattern suitable for climbing uphill or rapid acceleration.
In the power pattern, the shift down point and shift up point are set higher than those of the base pattern.
Shift Pattern Select Control Chart (1 Of 2). Scheme 1261
Shift Pattern Select Control Chart (2 Of 2). Scheme 1262
Base Pattern To Power Pattern. Scheme 1263
Depending on throttle opening and vehicle speed, 16 areas as shown in the figure are set. Accelerator depression speed for pattern changeover is set for each area.
When the accelerator depression speed exceeds this set value, the pattern changes from base to power.
Base Pattern To Power Pattern - Pattern Changeover. Scheme 1264
Power Pattern To Base Pattern
The power pattern is shifted to the base pattern, depending on car speed. Shifting to the base pattern is determined by the throttle position as shown in Figure below. Time lag in shifting is also determined by car speed. The maximum time lag is 3 seconds.
Power Pattern To Base Pattern. Scheme 1265
Reverse Inhibit Control
This control prevents the transmission from shifting into reverse when the select lever is accidentally placed in "R" range, protecting the components such as reverse clutch against damage.
If "R" range is selected during driving at a speed higher than the predetermined, the low clutch timing solenoid is energized.
Then, the pilot pressure is supplied to the reverse inhibit valve. This causes the reverse inhibit valve to move downward, closing the low & reverse brake port.
In this condition, the low & reverse brake does not engage since the ATF flowing from the manual valve is blocked by the reverse inhibit valve.
As a result, the transmission is put into Neutral, and the shifting into reverse is inhibited.
Reverse Inhibit Control. Scheme 1266
Grade Control
While a vehicle is driving up a hill, gear position is fixed to 3rd gear for avoiding busy up and down shift between 3rd - 4th gears.
When a vehicle is descending a steep hill under the designated vehicle speed (approximately 50 miles/hour), 4th gear downshifts to 3rd gear automatically by depressing the brake pedal.
This gearshift control is released by re-accelerating with depressing the accelerator pedal.
These controls are doing this based on the combination of throttle opening angle, engine speed, vehicle speed and so on.
Grade Control Chart (1 Of 2). Scheme 1267
Grade Control Chart (2 Of 2). Scheme 1268
Learning Control
This transmission is provided with a learning control function which allows the transmission hydraulic pressure to be so controlled that the transmission makes a shift at the optimum shifting point according to the vehicle conditions.
For this reason, there may be cases where shift shocks larger after the power supply is once interrupted (disconnection of battery terminal, flat battery, etc) or immediately after the ATF is replaced.
Once power supply is interrupted, the hydraulic pressure correction values so far learned and stored are erased and the system is initialized (reset to the new vehicle conditions).
The system starts the learning again as soon as the power supply is restored, and after driving for a while, the transmission becomes shiftable at the optimum shifting points.
Lager shift shocks immediately after ATF change are caused by the change in friction characteristics of the transmission internal parts.
Also in this case, therefore, the transmission becomes shiftable at the optimum shifting points after driving for a while.
AWD Transfer Clutch Control Chart (1 Of 2). Scheme 1269
AWD Transfer Clutch Control Chart (2 Of 2). Scheme 1270
Transfer Control
The transfer hydraulic pressure control module is fitted with the transfer valve body attached to the rear end face of the transmission case via separate plate.
The hydraulic oil of the transfer hydraulic pressure control module is led from the oil pump delivery pressure circuit on the transmission case front to the transmission case rear. From there it is further fed to the hydraulic circuit of the transfer valve body.
The hydraulic oil pressure (line pressure) is regulated by the transfer duty solenoid and transfer control valve for obtaining optimum rear torque distribution corresponding to the driving conditions.
Scheme 1271
- The pilot pressure is regulated to the transfer duty pressure by the transfer duty solenoid whose duty ratio is controlled by the TCM corresponding to the driving condition. (The transfer duty pressure varies with the degree of duty control.)
- The transfer duty pressure is applied to the transfer control valve.
- The line pressure is led also to the transfer control valve where the pressure is regulated to the transfer clutch pressure by the transfer duty pressure. (The transfer clutch pressure varies with the transfer duty pressure.)
- The transfer clutch pressure is applied to the transfer clutch and causes the clutch to be engaged.
- In this way, the transfer clutch pressure is varied so that optimum rear torque distribution can be achieved which corresponds to the vehicle driving conditions. (Scheme 1271): Transfer Control
The on-board diagnostics system is capable of detecting any trouble which has occurred in any of the following input and output signal systems.
On-Board Diagnostics System - Function. Scheme 1272
The results of on-board diagnostics are displayed by flashing ATF Temperature indicator light.
- Repeated flashing at 4 Hz ...Error such as battery trouble
- Repeated flashing at 2 Hz ...Normal
- Output of trouble code ...Check faulty portion
- Continued lighting of light ...Error in inhibitor switch, idle switch, or wiring
Select Monitor
Various data and ON/OFF signals being processed in the TCM can be monitored by connecting the select monitor to the select monitor terminal located under the instrument panel.
FAIL-SAFE FUNCTION
A fail-safe function is provided to maintain driveability even if trouble should occur in the vehicle speed sensor, throttle position sensor, inhibitor switch, or any of the solenoids.
Scheme 1273
- VEHICLE SPEED SENSOR 1 AND 2 A dual speed-sensing system is used. The speed signal is taken from the transmission (output shaft speed sensor). Even if one sensor system fails, the vehicle can be controlled normally with the other sensor system. If both front and rear vehicle speed sensor become faulty, the vehicle is made driveable in the 1st and 3rd speeds.
- THROTTLE POSITION SENSOR If throttle position sensor becomes faulty, the throttle opening is fixed at the preset angle.
- INHIBITOR SWITCH If the plural number of signals are inputted simultaneously due to inhibitor switch failure, the TCM makes it possible to drive the vehicle in the following conditions. Order of priority: D > N (P) > R > 3 > 2 > 1 > (Scheme 1273): Inhibitor Switch Failure, Fail-Safe Function Chart
- SHIFT SOLENOID 1 AND 2 If trouble occurs in either of solenoids 1 and 2, both solenoids are turned OFF, and the vehicle is made driveable in the 3rd hold range. If both solenoids should fail, the mechanical hydraulic circuit is used.
- LINE PRESSURE DUTY SOLENOID If line pressure duty solenoid fails, the solenoid is turned OFF and line pressure is raised to maximum to enable vehicle operation. And the vehicle is made driveable in the 1st and 3rd speeds.
- LOCK-UP DUTY SOLENOID If lock-up duty solenoid fails, the solenoid is turned OFF and lock-up is released.
- TRANSFER DUTY SOLENOID When the transfer duty solenoid becomes inoperative, it turns OFF. This causes maximum oil pressure to be applied to the transfer clutch so that the power is always transmitted to rear axles. (Direct-coupling AWD)
- 2-4 BRAKE DUTY SOLENOID If any trouble occurs in the 2-4 brake duty solenoid, the solenoid is turned off and the vehicle is made drivable in the 1st and 3rd speeds.
- LOW-CLUTCH TIMING SOLENOID If any trouble occurs in the low clutch timing solenoid, the solenoid is turned off and the vehicle is made drivable in the 1st and 3rd speeds.
- 2-4 BRAKE TIMING SOLENOID If any trouble occurs in the 2-4 brake timing solenoid, the solenoid is turned off and the vehicle is made drivable in the 1st and 3rd speeds.