Transaxle Electronic Control System
Transaxle Description
The automatic transmission used in the vehicle is a new development.
It is a fully automatic, electronically controlled 5-speed transmission designed for Front Wheel Drive (FWD) vehicles.
Its abbreviated designation FNR5 means:
- FN - front-wheel drive
- R - Model designation
- 5 - 5-speed transmission
The individual ratios are achieved through 2 planetary gear sets, connected one behind the other.
The individual components of the planetary gear sets are driven or held by means of 3 multi-plate clutches, a multi-plate brake, a brake band and a roller one-way clutch.
The torque is transmitted to the final drive assembly through an intermediate gear stage.
FNR5 Automatic Transmission Fluid is the transmission fluid specified for the FNR5 transaxle. The transmission fluid is changed as directed by the Scheduled Maintenance Guide that is supplied with the vehicle.
The selector lever gives the driver a choice of P, R, N, D and L.
The default gear for this transaxle is 3rd gear.
To minimize fuel consumption, the torque converter lock-up clutch is closed by the Transmission Control Module (TCM) in 3rd, 4th and 5th gears depending on the throttle position and vehicle speed.
The transmission has electronic synchronous shift control, which guarantees extremely smooth gear shifting over the entire life of the transmission.
A hydraulic emergency operating program maintains limited operation in the event of failure of important electrical components.
The transmission can be tested using a scan tool through the Data Link Connector (DLC) in the passenger compartment.
Identification Tags
When servicing the automatic transaxle, refer to the identification tag located on the case.
Range Selection
The transaxle range selector has 5 positions: P, R, N, D and L.
Selector Lever Position P
In selector lever position P, no gear is selected. The parking pawl is engaged manually by the selector lever cable and the manual control lever.
For safety reasons, always apply the parking brake whenever the vehicle is parked.
Selector Lever Position R
In selector lever position R, reverse gear is selected. REVERSE allows the vehicle to be operated in a rearward direction, at a reduced gear ratio.
Selector Lever Position N
In selector lever position N, no gear is selected. The driveline is not locked, so the wheels are free to rotate.
The vehicle may be started in NEUTRAL.
Selector Lever Position D
In selector lever position D, the transmission control allows all the gears to be selected.
Selector Lever Position L
In selector lever position L, the transaxle provides more engine breaking when the accelerator pedal is released than in D.
If the selector lever is moved to position L at an excessive vehicle speed for 1st gear, the transmission control only allows the downshift to take place when the corresponding vehicle speed has been reached.
FNR5 Transaxle
Torque Converter and Torque Converter Lock-Up Clutch
The torque converter transmits engine torque hydraulically to the transmission input shaft.
The stator boosts the torque to the input shaft (approximately 85% difference in speed between the impeller and the turbine).
The stator is made of synthetic resin to reduce weight.
To increase the efficiency of the automatic transmission, the torque converter has an apply clutch. When the Torque Converter Clutch (TCC) is applied, the torque is transmitted directly from the crankshaft through the torque converter housing to the transmission input shaft.
The TCC is applied hydraulically by the TCM by means of the solenoid valves in the valve body in 3rd, 4th and 5th gears. Apply is dependent on the throttle position, vehicle speed and manual selector lever position.
Valve Body
The valve body contains 8 solenoid valves:
- three PWM solenoid valves.
- three shift solenoid (on/off) valves.
- two main regulating valve pressure control solenoids.
The individual clutches and bands are supplied pressure from the PWM solenoid valves and the shift solenoid (on/off) valves and thus the gears are shifted.
The PWM solenoid valves allow direct actuation of the clutches and bands to make sure of extremely smooth shifting through precise pressure regulation.
The shift solenoid (on/off) valves switch the hydraulic path to the clutches and bands, reducing the number of required modulating valves.
The main regulating valve (Variable Force Solenoid (VFS)) makes sure that sufficient hydraulic pressure is available in all operating conditions.
Pulse-Width Modulation (PWM) Solenoid Valves
PWM solenoid valves control the pressure to the bands and clutches.
Shift Solenoid (On/Off) Valves
The shift solenoid (on/off) valves switch the different transmission fluid passages in the valve body to direct the pressure to the individual clutches and bands.
The shift solenoid valves are needed for direct actuation of the individual clutches and bands.
Main Regulating Valves
The main regulating valve (pressure control solenoids) control the required main line pressure for the individual transmission ranges.
The main line pressure is controlled dependent on the current engine load.
Shift Solenoids, Shift Solenoid A (SSA), Shift Solenoid B (SSB) and Shift Solenoid C (SSC)
Pulse-Width Modulation (PWM)
The PWM type shift solenoids adjust the amount of output pressure according to the signal from the TCM and controls the pressure of each clutch.
With no electrical current supplied to the solenoids, the supply port (line pressure) in the solenoid opens and is engaged with the output port (clutch pressure). As a result, hydraulic pressure is supplied to the hydraulic passage for the clutch pressure.
With electrical current supplied to the solenoids, the supply port (line pressure) in the solenoid closes and the output port (clutch pressure) and the drain port are engaged to drain the clutch pressure.
Shift Solenoids, Shift Solenoid D (SSD), Shift Solenoid E (SSE) and Shift Solenoid F (SSF)
On/Off Solenoids
OFF: With no electrical current supplied to the solenoids, the output port and the drain port are engaged in the solenoid and the output pressure is drained.
ON: With electrical current supplied to the solenoids, the output port and the supply port are engaged in the solenoid and the output pressures become equivalent to the solenoid reducing pressure.
Pressure Control Solenoid A (PCA)
The PCA has a high stability in hydraulic pressure that has been adopted for the line pressure control.
Because the pressure control solenoid controls the hydraulic pressure according to the electrical current value, the degree of freedom in control increases. The controllability is maintained even under aeration and pressure variation can be reduced.
By changing the electrical current value (0-1 amp) inside the solenoid, the PCA adjusts the hold power of the hold pressure valve, controlling the pressure to the prescribed hydraulic pressure.
Pressure Control Solenoid B (PCB)
The on/off type shift solenoid adjusts the amount of output pressure according to the signal from the TCM and controls the pressure of each clutch.
One-Way Clutch (OWC) No. 1
The One-Way Clutch (OWC) outer race rotates clockwise freely, but the sprags rise to lock the rotation when the outer race tries to rotate counterclockwise. The OWC locks the counterclockwise rotation of the front internal gear and also locks the counterclockwise revolution of the rear planetary via the rear planetary carrier.
One-Way Clutch (OWC) No. 2
The OWC outer race rotates counterclockwise freely, however the roller moves to the right and locks the rotation when it tries to rotate clockwise. The OWC locks the clockwise rotation of the direct clutch and also locks the clockwise rotation of the secondary sun gear via the direct clutch.
External Selector Lever Mechanism
The transmission end of the selector lever cable is attached to a ball on the manual control lever.
The cable abutments are secured to the transmission housing, and then to the bracket of the manual control lever.
The adjuster for the selector lever cable is located at the transmission side of the cable.
At the selector lever end, the cable is clipped onto a ball.
Overview Transmission Control
Transmission Control Module (TCM)
The TCM is located under the instrument panel on the LH side.
On vehicles with automatic transaxles, the TCM controls the transaxle. In this case, a module with 16- and 24-pin connectors is used.
The TCM evaluates the incoming signals from the individual sensors and actuates the solenoid valves in the valve body of the transaxle directly according to the operating state.
Diagnostic checks can be carried out on the transmission through the DLC above the Central Junction Box (CJB).
Emergency Operating Program
If correct shifting can no longer be guaranteed due to failure of certain signals, the TCM changes to an emergency operating program.
The driver is informed of the operation of the emergency operating program by the illumination of the powertrain warning indicator in the Instrument Cluster (IC).
Continued motoring is guaranteed in the following limited conditions:
- Maximum main line pressure
- 3rd gear in selector lever positions D, 2 and 1 without the TCC
- REVERSE gear in selector lever position R
Electronic Synchronous Shift Control
Control of Shift Operations
During a shift operation, certain elements are released while others are actuated. Ideally, this process takes place simultaneously (synchronously) to avoid jerky shifting.
The time for the shift operation should remain within the time limits provided.
When the shift operation is controlled conventionally, the pressure buildup and reduction at the shift elements are set and defined for ideal conditions (synchronous shifting).
As there is no way of influencing the control in the event of different levels of wear in the shift elements, when the transaxle has been used for a fairly high mileage it is possible that the pressure buildup and reduction may no longer be synchronous.
The result or premature pressure reduction at the element to be switched OFF is an unwanted rise in the Turbine Shaft Speed (TSS) as the element to be switched ON cannot transmit the input torque.
The result of delayed pressure reduction at the element to be switched OFF is an unwanted decrease in the TSS as both shift elements transmit the input torque. In the process, the torque is transmitted to the transmission housing through internal locking.
In both cases, a jerk will be felt during the shift operation.
In addition, wear in the shift elements leads to a lengthening of the shift operation. Therefore, shifting takes longer when the transaxle has accumulated a higher mileage.
Control of Shift Operations With Electronic Synchronous Shift Control
In the automatic transaxle, electronic synchronous shift control is used.
Electronic synchronous shift control monitors the shift operations and is able to adapt to the wear in the shift elements over the life of the transaxle.
This is possible since the shift elements are actuated by modulating valves.
The system monitors the shift time whether the shift operation is synchronous.
If the TCM detects a deviation from the stored values for the shift time and synchronization of the shift operation, the pressure buildup or reduction is adapted accordingly.
Throttle Position (TP) Sensor
The Throttle Position (TP) sensor is located on the Throttle Body (TB).
It supplies information to the PCM about the position of the throttle plate. The TCM receives the signal from the PCM.
It also detects the speed of actuation of the throttle plate.
The TCM uses the signals for the following functions, among other things:
- to determine the shift timing.
- to control the main line pressure.
- to control the TCC.
- for kickdown.
In case of absence of the TP signal, the engine control uses the signals of the Mass Air Flow (MAF) and Intake Air Temperature (IAT) sensors as a substitute signal. The main line pressure is increased and hard shifts may occur.
Mass Air Flow (MAF) and Intake Air Temperature (IAT) Sensor
The Mass Air Flow (MAF) sensor is located between the air cleaner housing and the air intake hose leading to the throttle housing.
The Intake Air Temperature (IAT) sensor is incorporated in the housing of the MAF sensor.
The MAF sensor, in conjunction with the IAT sensor, provides the PCM with the primary load signal.
The TCM receives the signals from the PCM and uses them for the following functions, among other things:
- to control the shift operations.
- to control the main line pressure.
If the MAF sensor fails, the signal of the TP sensor is used as a substitute.
Crankshaft Position (CKP) Sensor
The Crankshaft Position (CKP) sensor is located on the engine/transmission flange.
The CKP sensor is an inductive sensor which provides the PCM with information about the engine speed and position of the crankshaft.
The TCM receives the signals from the PCM and uses them for the following functions among other things:
- to control the TCC.
- to check the torque converter slip.
- to control the main line pressure.
No substitute signal is available for the CKP sensor. If the signal is not present, the engine stops.
Output Shaft Speed (OSS), Intermediate Shaft Speed and Turbine Shaft Speed (TSS) Sensors
Turbine Shaft Speed (TSS) Sensor
The Turbine Shaft Speed (TSS) sensor is located on the transaxle housing over the input shaft.
The TSS sensor is an inductive sensor which senses the speed of rotation of the input shaft.
The signal is used for the following functions:
- to control the shift operations.
- to control the TCC.
- to check the torque converter slip.
If the TSS sensor fails, the signal of the Output Shaft Speed (OSS) sensor is used as a substitute signal.
Intermediate Shaft Speed Sensor
The intermediate shaft speed sensor is located on the transaxle housing over the intermediate shaft.
The intermediate shaft speed sensor is an inductive sensor which senses the speed of rotation of the intermediate shaft.
The signal is used for the following functions:
- to determine the shift timing.
- to control the shift operations.
- to control the TCC.
If the intermediate shaft speed sensor fails, the signals of the OSS and TSS sensors are used as a substitute signal.
Output Shaft Speed (OSS) Sensor
The OSS sensor is located in the transaxle housing above the rotor in the differential.
The OSS sensor is an inductive sensor which detects the vehicle speed by means of a rotor on the differential.
The signal is used for the following functions among other things:
- to determine the shift timing,
- to supply the vehicle speed input signal for the TCM.
If the OSS sensor fails, the signal of the TSS sensor is used as a substitute signal.
Transmission Range (TR) Sensor
The Transmission Range (TR) sensor is located on the manual control lever shaft on the transaxle housing.
When the manual control lever shaft is moved by means of the selector lever cable, an engagement pin in the inner ring of the TR sensor moves through the different positions. The signals are transmitted to the TCM, the reversing lamps and the starter inhibitor relay.
NOTE: Correct operation of the TR sensor is only guaranteed when the manual selector lever cable is adjusted correctly.
The signals of the TR sensor are used for the following functions:
- to recognize the selector lever position.
- to actuate the starter inhibitor relay.
- to actuate the reversing lamps.
No substitute signal is available for the TR sensor.
If the connection is cut, the vehicle cannot be started.
Brake Pedal Position (BPP) Switch
The Brake Pedal Position (BPP) switch is mounted on the brake pedal bracket.
It switches the stoplights on and tells the PCM when the brakes are applied.
The signal of the Brake Pedal Position (BPP) switch is received by the TCM from the PCM and used for the following functions:
- to release the TCC when the brake pedal is depressed.
- to switch off the selector lever shift lock when the brake pedal is depressed in P.
No substitute signal is available for the BPP switch.
If the connection to the BPP switch is cut, the selector lever cannot be moved out of P.
Transmission Fluid Temperature (TFT) Sensor
The Transmission Fluid Temperature (TFT) sensor is located on the internal wiring harness to the solenoid valves in the transmission fluid pan.
It is a resistor and measures the transmission fluid temperature.
The TFT is used by the TCM for the following functions:
- applying the TCC is not permitted until the transmission fluid reaches a certain temperature.
- engagement of 4th gear is prevented in extreme sub-zero temperatures until the normal operating temperature is reached.
- if the transmission fluid temperature is excessive, a pre-set fixed shift curve is selected and the TCC is closed in 2, 3, 4 and 5; of the transmission warning indicator is activated. No substitute signal is available for the TFT sensor.
Brake Shift Interlock Actuator (BSIA)
When the ignition is switched ON, the selector lever Brake Shift Interlock Actuator (BSIA) is actuated by depressing the brake (signal from the BPP switch). This retracts the locking pin so that the selector lever can be moved out of position P.
Substitute Function
If the brake pedal should fail due to malfunction, manual unlocking is possible.
For this, the cover of the release mechanism must be removed and a suitable object (ignition key) pressed into the opening until the selector lever can be moved out of position P.
NOTE: If P is selected again, the selector lever is locked again.
A/C
If the PCM registers a kickdown signal (Wide Open Throttle (WOT), throttle plate opened 95%), the A/C is switched OFF for a maximum of 15 seconds.
Starter Inhibitor Relay
The relay prevents the engine starting in manual selector lever positions R, D and L.
The relay obtains the information about the position of the selector lever directly from the TR sensor.
Ignition Key Lock Solenoid
The solenoid is incorporated in the ignition lock. In selector lever position P the ground connection to the solenoid is cut. The locking pin does not engage in the ignition lock.
In all the other selector lever positions, the ground connection to the solenoid is closed and the locking pin engages in the ignition lock.
When the manual selector lever is not in position P, removal of the ignition key is prevented.
Powertrain Warning Indicator
The powertrain warning indicator is located in the instrument cluster and is colored orange.
This indicator lights to tell the driver that the transmission control has switched to the emergency operating program or that the transmission fluid temperature is too high.