Mitsubishi Eclipse. Technical Information Manual (1994) - part 48

POWER TRAIN 

 Automatic Transaxle

here

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End of the

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sensor counts

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 position switch

Input Speed Sensor

The input speed sensor gives information, to the TCM, on

how fast the torque converter turbine is spinning. The sensor
is located on the front side of the transaxle case, close to

the bell housing. Even though the sensor is called the input
speed sensor, the sensor is actually generating a signal from
the torque converter turbine through the input clutch hub. The
torque converter turbine and input clutch hub are splined togeth-
er through the input shaft. The information supplied to the
TCM from the input sensor is compared to the output shaft
signal and the engine speed signal to determine planetary

 operating ratio, torque converter clutch slippage, torque

converter element speed ratio, torque capacity, etc. The rate
of input speed change is calculated and used in controlling
shifts.

Output Speed Sensor
The output speed sensor is located on the same side of the
transaxle case as the input speed sensor, but much closer

to the end of the transaxle. The output speed sensor generates
a signal from the rotation of the rear planetary carrier assembly.
When the output speed sensor signal is received by the TCM,
the signal is compared to the input speed signal to deternmine

gear ratio, detect clutch slippage, etc. It is also compared to

the throttie signal to determine shift points.
The output speed sensor is also used as the input for calculating
vehicle speed to the Powertrain Control Module (PCM). The

 transaxle does not have a vehicle speed sensor as

in other applications. The output speed signal is a direct input

to the TCM and is sent across the CCD bus for use by other
control modules.

Transmission Range and Park Neutral Position Switches
The transmission range switch is mounted to the case in the
valve body area. The input from the switch along with the

park neutral position switch tells the TCM what gear range

was selected by the driver. The TCM uses this input to determine
what gear range and shift pattern to use. The park neutral

position switch operates the starter relay and both the park 
neutral position and transmission range switches operate the
back up lamp relay. The park neutral position switch does
not allow starter engagement in any positions other than Park
“P” or Neutral “N”. Both switches must be closed to operate
the back-up lamps.

POWER TRAIN   Automatic Transaxle

Solenoid and

Pressure Switches

The low/reverse, overdrive, and 2-4 pressure switches are
all located in the solenoid pack assembly. All three switches
send the same type of information to the TCM. These switches
tell the TCM if there is hydraulic pressure in their particular
circuits. The pressure switches do not tell the TCM how much

pressure is in the circuit. They just indicate that pressure exists
or does not exist. This information verifies that the solenoids
are operating correctly and what gear the transaxle is in. The
switches open at approximately 11 psi and close at approximate-
ly 23 psi.

Engine Coolant Temperature Sensor

This engine coolant temperature sensor tells the TCM the tem-
perature of the engine. When the engine is cold, the TCM

may delay upshifts slightly to improve vehicle driveability. The

TCM prevents the torque converter clutch from engaging until
the engine warms up to normal operating temperature. If the
engine temperature is too high in any forward position, the
TCM engages the torque converter clutch in second, third,
or fourth gears to help cool the engine and prevent the transaxle
from overheating.

Brake Switch

The brake switch signal is used to make sure the torque convert-
er clutch is disengaged when the brakes are applied. It is
also used to cancel cruise control so that braking can occur.

POWER TRAIN 

 Automatic Transaxle

Engine Speed

The TCM uses both direct engine speed input from the crank-
shaft position sensor or distributor and calculated engine speed

input from the PCM over the CCD bus. The direct input is
required to provide immediate information for use by the TCM
control logic. The slower CCD engine speed data is used by

the TCM fail-safe logic to confirm that the direct engine speed
data is valid.

Speed Control Switch

The speed control on/off switch modifies the shift pattern when
a speed control “on” signal is received by allowing a torque
converter clutch engagement or disengagement, as well as

 shifts.

Manifold Absolute Pressure Sensor (MAP)

The MAP sensor provides engine load input and output torque

load on the input shaft to the TCM. These signals are sent
across the CCD bus to the TCM. The TCM uses this information
to modify shifting and reduce 3-4 shift hunting on grades.

POWER TRAIN 

 Automatic Transaxle

TRANSMISSION CONTROL MODULE OUTPUT SIGNALS AND DEVICES
The TCM takes the input information from the 

sembly. The following items are output components

sors, evaluates the input, then uses it to control

operated by the TCM.

the transmission control relay and the solenoid 

Transmission Control Relay

Solenoid and pressure

The instant the ignition is turned on, the TCM performs a self-test
to determine if its internal electronic circuits are all working
properly. If the self-test results are good, the TCM sends battery
voltage to the transmission control relay. The relay closes its

internal contacts which then supply battery voltage to the TCM
(confirms function of the relay), the four solenoids and the

three pressure switches in the solenoid assembly. If the TCM
“sees” a problem in the system, it turns off the power feed
to the transmission control relay, causing the contacts to open.
A diagnostic trouble code is then stored in memory. The trans-

mission control relay is located in various places depending
on the vehicle model. It can be located directly on the TCM

or in the harness near the TCM.

Solenoid Assembly
When the transmission control relay contact points are closed,

the solenoid assembly receives electrical power. The TCM
can now operate the solenoids, as determined by its program-

ming. The relay provides power to all four solenoids through
a single wire. This means that all the solenoids have voltage
supplied to them whenever the transmission control relay is
closed. The solenoids, however, are not energized until the

TCM grounds the solenoid return wire for the solenoid that

is needed.

Power and Ground

The ground wire from each solenoid goes back to the TCM.
The TCM energlizes each solenoid by connecting the solenoid

return wire to ground. Four of the wires in the 

 solenoid

assembly connector are solenoid return wires. Three wires
are for each pressure switch, and the last wire is the battery
feed wire from the transmission control relay. The TCM controls
both the power feed (through the transmission control relay)
and the ground to each solenoid (through the return wires).