Mitsubishi Eclipse. Technical Information Manual (1994) - part 50

POWER TRAIN   Automatic Transaxle

Transaxle Temperature
The transaxle temperature operating range is based

 predicted fluid temperature which is calculated

from a combination of inputs. The predicted fluid
temperature is continually updated and retained in

memory for 20 minutes after the ignition switch is

turned off. When the vehicle is started after an ex-
tended off time, the predicted fluid temperature is

reinitialized at a value equal to the battery tempera-

ture signal received from the PCM over the CCD
bus. The temperature input signal must then be

Transaxle Temperature Output Modes
Output modes used by the TCM are extreme cold,
supercold, cold, warm or hot. The extreme cold

range is set when the initial predicted fluid tempera-

ture is less than

 15 degrees   It will clear two

minutes after a cold start. The supercold range is

set when the predicted fluid temperature is less
than 0 degrees F. It will clear when the predicted
fluid temperature exceeds 10 degrees F. The 

Shift Schedule Logic
Shift schedule logic, programmed into the TCM,
selects the appropriate shift schedules for the cur-
rent operating conditions. This is to determine the
“desired” gear range the transaxle must be operated
in. The desired gear range is a primary input to
the shift logic selection function. The TCM then acti-
vates the appropriate shift logic schedule to achieve

the desired gear. The actual shift points within each

shift schedule have been pre-determined for best
transaxle operation and are stored in the 

ROM memory.

calculated and then increased primarily based on
transaxle run time in gear. Time calculation excludes
operation in park and neutral.
A detailed explanation of how transaxle temperature

range affects transaxle operating characteristics is

covered in the shift schedule and EMCC sections.
The primary temperature inputs to the TCM are

battery temperature, engine coolant temperature
and in-gear run time since start-up.

cold range allows for near normal transaxle opera-
tion under sub-zero conditions. The cold, warm,
and hot ranges provide different operating features
as warm-up occurs. The transaxle temperature
range is “cold” at less than 36 degrees F, “warm”
above 40 degrees F and “hot” above 80 degrees
F.

The primary inputs to the TCM are the transmission

range and park neutral position switches (shift lever
position), throttle position, and output speed. Some

other secondary inputs include, but are not limited
to, calculated transaxle temperature and current
shift logic.
Shift schedule output codes simply provide the TCM
with the desired operating gear range signal. Shift
schedule logic output is updated every 7 millisec-
onds and is a primary input to the Shift Logic Selec-
tion function programmed into the TCM.

POWER TRAIN 

 Automatic Transaxle

Inhibits and Shift Action Summary

For neutral (N) and reverse (R) there are no logic
inhibits placed on SLP changes into or out of either
neutral or reverse. These gear ranges are shift lever

controlled modes of operation. Neutral and reverse

must be immediately provided for. Also, a reverse
block function is used at speeds over approximately
10   15 mph by continuously venting the Low/Re-

verse (L/R) clutch. The 

 clutch is also vented

at speeds over 8 mph in neutral.

For drive (D), Second (2) or low (L), when speed
ratio or pressure switch errors occur during transaxle
use, the TCM will maintain the current gear range

to prevent potentially hazardous gear selection.
A separate set of shift schedules exist for each
engine/transaxle application. The TCM knows which
set of shift schedules to use by looking at the PCM

 over the CCD bus. The engine and

 

 Cold, Warm or Hot

The “D” schedule provides first, second, third and
fourth gears. This shift schedule is selected when
SLP   “D” and the transaxle calculated temperature

range is cold, warm or hot. It should be noted that

the 

 schedule will delay the 3-4 upshift, and will

body identifications are retained in the 
memory to ensure that the correct schedule is used
if the CCD bus fails.

There are four different shift schedules within each
engine set. They are selected primarily by the Shift

Lever Position input code and the transaxle operat-
ing temperature range that is calculated. Separate

shift schedules exist for the following; Shift Lever

Position 

D, Shift Lever Position   D (supercold

temperature range), and Shift Lever Position   L.
A typical set of shift schedules have been plotted
out in graph form. These have been modified 
clarity. The shift schedules primarily use throttle
angle and output shaft speed as the determining
factors. The main difference between these sched-

ules are as follows:

cause earlier 4-3 downshifts when the transaxle
temperature range is cold. Throttle input is also
limited to prevent high engine speeds with a cold
engine.

 

 (Supercold and Extreme Temperature Range)

The supercold 

 schedule is a revised D schedule.

It is selected whenever the initial calculated trans-

axle temperature is less than 0 degrees F. This

revised schedule prevents closely spaced shifts and
part throttle kickdowns. This results in delayed (high-

er speed) upshifts, earlier closed throttle downshifts,
and in most cases the inability to obtain either 4-2
or 3-1 kickdowns. The primary reason is to allow

more time for clutch pressures to achieve their nor-
mal in-gear condition after a shift. This should hap-
pen before the next shift occurs to avoid clutch
overlap (two clutches applied at the same time).

If the calculated transaxle temperature at start-up

is in the extreme cold range of   15 degrees F.
or less, all the solenoids will be held off. Also, the
pressure switch and speed sensor checks will 
disabled. This action provides the same mode of
operation as with limp-in or default (second gear
operation only, in any forward gear range selection).

This is done to prevent clutch damage and inadver-
tent shutdowns by delaying all TCM operation until
supercold conditions can be met.

    L

The L schedule also has 1-2 and 2-3 shifts but
they are much more delayed. The determining factor
for this schedule is that engine speed is monitored
and shifts occur at peak engine RPM. Even though
the driver has selected the low position, the shift
schedule is designed to upshift the transaxle at 

per level engine RPM to protect the engine from
over-speed. Downshifts also occur at higher vehicle

speeds. This is done to provide the highest gear

ratio for maximum engine braking when descending

steep grades.

POWER TRAIN 

 Automatic Transaxle

Adaptive Coast Down Scheduling
Adaptive scheduling may result in delayed 4-3 or
3-2 downshifts under certain conditions in order

Speed Control
When the transmission temperature range is either
warm or hot, the 4-3 shift pattern is modified to

 earlier if a cruise control “on” signal is

received over the CCD bus from the PCM. If the

Manifold Absolute Pressure (MAP)

This signal is used to calculate changes in engine
output torque to the input shaft of the transaxle.
This information is used by the TCM to improve

Throttle Failure
A throttle default value of 25 degrees throttle opening

is substituted to provide reasonable driveability.

Third gear is substituted for fourth to provide a 

CCD Bus Failure

The initial predicted fluid temperature is based on
the battery temperature after an extended time off.

It is important to understand that if this data becomes
invalid (out of normal range or the CCD bus fails),

the TCM will substitute -3 degrees F. for ambient
temperature. This is done because the control logic
for the colder temperature range is designed to
tolerate an actual warmer transaxle. Some of the

Loss of Prime Protection

Special logic is included in the fail safe routines
to identify a loss of oil pump prime. A no pressure
condition is usually due to a low fluid level and

typically occurs following hard braking or cornering.
This will cause the oil filter to be exposed to air.

 

 

 

 

to maintain good shift quality.

bus should fail, this logic will not be initiated with
speed control “on”, and the vehicle may lose more

speed and not kick down on grades.

shift quality and reduce 3-4 shift hunting on steeper

road grades. A loss of this signal will cancel grade
hunting detection logic.

able performance level. Throttle induced kickdowns
will become unavailable, but selection of drive and
low shift lever operation remains normal.

effects of this are as follows; Defaults are possible

if the actual transaxle temperature is within the ex-

treme cold range. The 3-4 shift will occur at a higher
speed for approximately the first minute of operation

in-gear (see supercold 

 shift schedule). A reduc-

tion in upshift shift quality is possible for approxi-

mately 4 minutes if the actual transaxle temperature
is in the warm to hot range.

The result will be a loss of oil pump prime and
possibly a no drive condition. The special logic pre-
vents the inappropriate setting of diagnostic trouble
code.

Torque Converter EMCC Logic
The use of partial Electronically Modulated Converter
Clutch (EMCC) is available at speeds as low as 17

mph, giving the advantage of improved fuel economy

while buffering the rest of the power-train from engine
firing pulses. Full EMCC is utilized under certain
conditions to improve gas mileage. Both full EMCC
or partial EMCC may also be scheduled to help reduce

heat build-up of the transaxle or its fluid under certain

driving conditions.
Torque converter full EMCC and partial EMCC avail-
ability depends on many different input conditions.
These include shift lever position (D, 2, L), current
gear range (second, third, or fourth), engine coolant
temperature, input speed, and throttle angle.
The outputs controlling the torque converter are; No’

EMCC, Partial EMCC, Full EMCC and Gradual to
No EMCC. The boxes in the chart represent the

four EMCC logic states.

POWER TRAIN

 - Automatic Transaxle

Types of EMCC Logic

No EMCC Logic -This is when the torque converter

clutch is off.

Partial EMCC Logic   This logic will modulate the

 solenoid (duty-cycle) to obtain partial torque

converter clutch application. Partial EMCC operation

Full EMCC Logic   This increases the 

 sole-

noid duty-cycle to full 

 after partial EMCC control

brings the engine speed to within the desired slip

Gradual to No EMCC from Full or Partial Logic 
This logic is designed to soften the change from

Full or Partial EMCC to No EMCC, at mid-throttle,

EMCC Fail-safe

A malfunction of the EMCC system is detected from
a lengthy partial EMCC operation near the maximum
allowable duty-cycle, except at heavy throttle. If a
diagnostic trouble code is reported, the TCM will

EMCC Break-in Procedure

With the vehicles odometer reading from 0 to 500

miles, there will be no torque converter EMCC. From
500 to 1500 miles, the TCM will gradually decrease
EMCC from a 200 rpm slip to a 60 rpm slip. When

vehicle mileage is above the EMCC break-in period
and a malfunction occurs with the torque converter,

EMCC Inhibits

The TCM is provided with EMCC inhibits to prevent

EMCC from occurring under specific conditions. The

following are times when EMCC will not occur.

Transaxle Temperature   When the transaxle tem-

perature range is cold or supercold, EMCC is inhib-
ited (kept from occurring). In the event of a CCD
Bus failure, -3 degrees F. is substituted for the initial

Brake Signal (on)   This will cancel and prevent
EMCC as long as a brake signal is “on”. If a bus

failure occurs, the “brake on” signal is not received,
and EMCC is still possible.

Solenoid Switch Valve   If a solenoid switch valve
(SSV) malfunction is detected, EMCC will not occur.
A SSV diagnostic trouble code will only be stored

EMCC Fault

 Any reported EMCC diagnostic

trouble code will prevent any type of EMCC from
occurring.

is maintained until full EMCC logic is called for and
actuated.

range of transaxle input speed relative to engine
rpm (crankshaft speed).

by gradually decreasing the 

 solenoid 

cycle.

not operate the torque converter clutch. It will remain
unapplied until the next restart. Diagnostic trouble
code 38 will be stored in memory.

the new replacement torque converter must go
through the same EMCC break-in procedure. The
TCM must be re-programmed to allow for (restart)
the break-in period. To do this, use the scan tool

(MUT-II).

temperature. This initial value is incremented up
to normal engine operating temperature based on
engine running time. This will result in delayed

EMCC operation under start-up conditions.

Throttle Position Sensor   Any throttle value less
than 2 or 3 degrees (closed throttle) will cancel

EMCC. If a throttle position sensor failure is identified
by the TCM, EMCC will not occur.

if the transaxle operating temperature range is hot,
and the malfunction occurs at least three times.

The fault counter is reset during the start routine.