Torque Converter
Torque ConverterTorque Converter and Torque Converter Lock-Up Clutch
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 lock-up clutch is closed, the torque is transmitted directly from the crankshaft through the torque converter housing to the transmission input shaft.
The torque converter clutch is applied hydraulically by the PCM by means of the solenoid valves in the valve body in 3rd and 4th gears. Apply is dependent on the throttle position, vehicle speed and manual selector lever position.
Fluid Pump and Stator Support
Fluid Pump And Stator Support:
The fluid pump is a crescent gear pump and is driven directly from the crankshaft by means of drivers on the converter impeller hub. The fluid pump is bolted to the transmission housing.
The stator support is part of the fluid pump. Splines on the support locate and hold the converter stator.
Overview Transmission Control
Overview Transmission Control (Part 1):
Overview Transmission Control (Part 2):
Powertrain Control Module (PCM)
Powertrain Control Module (PCM):
The PCM is located under the trim panel on the right-hand A-pillar.
On vehicles with automatic transmissions, the EEC-V PCM controls the transmission in addition to the engine management system. In this case, a module with 104 pins is used.
The PCM evaluates the incoming signals from the individual sensors and actuates the solenoid valves in the valve body of the transmission directly according to the operating state.
Diagnostic checks can be carried out on the transmission through the data link connector (DLC) above the central junction box (CJB).
Emergency Operating Program
If correct gear shifting can no longer be guaranteed due to failure of certain signals, the PCM 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.
Continued motoring is guaranteed in the following limited conditions:
^ Maximum main line pressure
^ Third gear in manual selector lever positions D, 2 and 1 without the torque converter lock-up clutch
^ Reverse gear in manual selector lever position R
Electronic Synchronous Shift Control (ESSC)
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 gear 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 transmission 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 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 turbine shaft speed 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 transmission has accumulated a higher mileage.
Control of Shift Operations With ESSC
In the automatic transmission, electronic synchronous shift control (ESSC) is used.
ESSC monitors the shift operations and is able to adapt to the wear in the shift elements over the life of the transmission.
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 PCM 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.
It supplies the PCM with information about the position of the throttle plate.
It also detects the speed of actuation of the throttle plate.
The PCM uses the signals for the following functions among other things:
^ to determine the shift timing.
^ to control the main line pressure.
^ to control the torque converter lock-up clutch.
^ 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 MAF sensor is located between the air cleaner housing and the air intake hose leading to the throttle housing.
The 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 PCM uses the signals 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 signal is used for the following functions among other things:
^ to control the torque converter lock-up clutch.
^ 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.
Turbine Shaft Speed (TSS) Sensor
The turbine shaft speed (TSS) sensor is located in the transmission housing over the transmission input shaft.
The TSS sensor is an inductive sensor which senses the speed of rotation of the transmission input shaft.
The signal is used for the following functions:
^ to control the shift operations.
^ to control the torque converter clutch.
^ 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.
Output Shaft Speed (OSS) Sensor
Output Shaft Speed (OSS) Sensor:
The OSS sensor is located in the transmission 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 PCM.
If the OSS sensor fails, the signal of the TSS sensor is used as a substitute signal.
Transmission Range (TR) Sensor
Transmission Range (TR) Sensor:
The transmission range (TR) sensor is located on the manual shaft on the transmission housing.
When the manual shaft is moved by means of the manual 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 PCM, 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 manual 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.
Stoplamp Switch
The brake pedal position (BPP) switch is mounted on the brake pedal bracket.
It switches the stoplights on and tells the EEC-V PCM when the brakes are applied.
The signal of the stoplamp switch is used by the PCM for the following functions:
^ to release the torque converter lock-up clutch when the brake pedal is depressed.
^ to switch off the manual selector lever shift lock when the brake pedal is depressed in PARK.
No substitute signal is available for the BPP switch.
If the connection to the BPP switch is cut, the manual selector lever cannot be moved out of PARK.
Transmission Fluid Temperature (TFT) Sensor
The transmission fluid temperature (TFT) sensor is located on the internal wiring harness to the solenoid valves in the fluid pan.
It is a resistor and measures the transmission fluid temperature.
The transmission fluid temperature is used by the PCM for the following functions:
^ Applying the torque converter clutch 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 torque converter lock-up clutch is closed in 2, 3 and 4, and the transmission warning indicator is activated. No substitute signal is available for the TFT sensor.
Overdrive (O/D) Switch
Overdrive (O/D) Switch:
The O/D switch transmits a signal to the PCM to select or suppress 4th gear in manual selector lever position D.
The signal of the O/D switch is used for the following functions:
^ as an input signal to convey the driver's intent to the PCM.
^ to display the driver's intent with the O/D indicator in the instrument cluster.
No substitute signal is available for the O/D switch. If it should fail, it is always possible to shift into 4th gear in manual selector lever position D.
Manual Selector Lever Shift Lock Solenoid
Manual Selector Lever Shift Lock Solenoid:
When the ignition is switched on, the manual selector lever shift lock solenoid is actuated by depressing the brake (signal from the stoplamp switch). This retracts the locking pin so that the manual selector lever can be moved out of position P.
Substitute Function
Manual Selector Lever Shift Lock Solenoid:
Substitute Function:
NOTE: If P is selected again, the manual selector lever is locked again.
If the brake signal should fail due to a 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 manual selector lever can be moved out of position P.
Air Conditioning
If the PCM registers a kickdown signal (WOT, throttle plate opened 95%), the air conditioning 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, 2 and 1.
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 manual 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 manual 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.
O/D Indicator
The O/D indicator is located in the instrument cluster and is colored green.
It tells the driver that shifting into 4th gear is prevented by the transmission control.
The O/D light flashes to tell the driver that the transmission control has switched to the emergency operating program or that the transmission fluid temperature is too high.