FNR5 Automatic Transmission/Transaxle

Overview Transmission Control

Overview Transmission Control:

Overview Transmission Control:

Transmission Control Module (TCM):

Transmission Control Module (TCM)

The TCM is located under the instrument panel on the LH side.

On vehicles with automatic transmissions, the TCM controls the transmission. 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 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 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.

Continued motoring is guaranteed in these limited conditions:
^ Maximum main line pressure
^ 3rd gear in manual selector lever positions "D", "2" and "1" without the torque converter 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 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.

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 these functions, among other things:
^ to determine the shift timing.
^ to control the main line pressure.
^ to control the torque converter 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 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 these functions, among other things:
^ to control the shift operations.
^ to control the main line pressure.

If the MAF sensor fails, the signal of the throttle position (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 these functions among other things:
^ to control the torque converter 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.

Output Shaft Speed (OSS), Intermediate Shaft Speed and Turbine Shaft Speed (TSS) Sensors:

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 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 these 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.

Intermediate shaft speed sensor
The intermediate shaft speed sensor is located in the transmission housing over the transmission intermediate shaft.

The intermediate shaft speed sensor is an inductive sensor which senses the speed of rotation of the transmission input shaft.

The signal is used for these functions:
^ to determine the shift timing.
^ to control the shift operations.
^ to control the torque converter clutch.

If the intermediate shaft speed sensor fails, the signal of the output shaft speed and turbine shaft speed sensors is used as a substitute signal.

Output shaft speed (OSS) sensor
The output shaft speed (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 these 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:

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 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 these 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 received by the TCM from the PCM and used for these functions:
^ to release the torque converter clutch when the brake pedal is depressed.
^ to switch off the manual 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 manual 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 fluid pan.

It is a resistor and measures the transmission fluid temperature.

The transmission fluid temperature is used by the TCM for these 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 clutch is closed in "2", "3", "4" and "5"; of the transmission warning indicator is activated. No substitute signal is available for the TFT sensor.

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:

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 manual selector lever can be moved out of position "P".

NOTE: If "P" is selected again, the manual selector lever is locked again.

Air conditioning
If the PCM registers a kickdown signal (WOT, throttle plate opened 95 percent), 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" 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 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.

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.