POWER TRAIN
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Automatic Transaxle
Transaxle Temperature
The transaxle temperature operating range is based
ona
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
F.
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
super-
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
TCM’s
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.
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