lit tle lon ger before the next upshift. If the driving
st yle is still aggressive, the shift poin t is modified up
to ten st eps. If the driving returns to nor mal, then
the shift point modification a lso retu rns to the base
position .
This adaptation has no memory. Th e adaptation to
dr iving style is n othing m ore tha n a shift point mod-
ifica tion mea nt to assist an aggressive driver. The
sh ift points are adjusted for the m oment and return
to base position a s soon as t he input s are contr olled
in a more rat iona l ma nner.
Shift Time Adaptation (Shift Overlap Adaptation, Working
Pressure)
Sh ift tim e adapta tion is th e ability of the TCM to
electronica lly alter the time it takes to go from one
gear to anot her. Shift time is defined a s the time it
takes to disenga ge one shift member while anot her is
being a pplied. Sh ift t ime adapta tion is divided in to
four categories:
1. Acceleratin g u psh ift, which is a n upshift under
a load. For sh ift time adaptation for t he 1-2 u pshift
to take place, the transmission must shift from 1st to
2nd in six differen t engine load r anges vs. transmis-
sion outpu t speed r anges.
2. Decelerating u pshift, which is a n upshift u nder
no load. Th is shift is a rollin g upshift a nd is accom -
plished by letting the vehicle roll into the next gear.
3. Acceleratin g down shift, which is a downshift
under load. Th is shift can be in itiated by the throttle,
with or withou t kickdown. The shift selector ca n also
be u sed .
4. Decelerating down sh ift, wh ich is accom plished
by coasting down . As the speed of the vehicle
decreases, the transmission down sh ifts.
Fill Pressure Adaptation (Apply Pressure Adaptation, Modu-
lating Pressure)
Fill pressure adaptation is the ability of the TCM
to modify the pressure used to en gage a sh ift mem-
ber. The valu e of this pressu re determines how firm
the sh ift will be.
• If too m uch pressure is used, th e shift will be
hard.
• If t oo lit tle pressu re is used, the t ransmission
may slip.
The pressure adjustment is n eeded t o com pensate
for th e tolera nces of the shift pressu re solenoid va lve.
The am ount the solenoid va lve open s as well as how
quickly th e valve can move, has a n effect on the pr es-
su re. The return spring for the sh ift m ember pro-
vides a resista nce that must be overcom e by the
pr essu re in order for shift member to apply. Th ese
retu rn spr ings have slight ly different values. This
also affects th e application pr essure a nd is compen-
sa ted for by fill pressur e adapt ation.
Fill Time Adaptation (Engagement Time Adaptation)
Fill time is t he time it takes to fill t he piston cav-
ity an d take up any clear ances for a friction element
(clutch or bra ke). F ill time adaptation is the ability of
the TCM to modify the time it takes to fill t he shift
member by a pplyin g a preload pressu re.
CONTROLLER MODES OF OPERATION
Permanent Limp - In Mode
When the TCM det ermines th ere is a n on-recover-
able condition present that does not a llow proper
transmission oper ation, it places the transmission in
perma nent Limp-In Mode. When the condition occurs
the TCM turns off all solenoids as well as t he sole-
noid su pply output circuit. If this occurs while the
vehicle is movin g, t he tr ansmission rem ain s in the
curren t gea r position un til the ign ition is turned off
or th e shifter is placed in the “P” posit ion. When the
sh ifter has been pla ced in “P,” the transmission only
allows 2n d gear operat ion. If t his occu rs while the
vehicle is not moving, the tra nsmission only allows
operat ion in 2nd gear.
Temporary Limp - In Mode
This mode is the sa me a s the permanent Limp-In
Mode except if the condition is no longer present, the
system resumes n ormal operation.
Under Voltage Limp - In Mode
When the TCM detects th at system voltage ha s
dr opped below 8.5 volt s, it disa bles volt age-depen-
da nt diagnostics and pla ces the tran sm ission in the
temporary Limp-In Mode. When the TCM senses
that the volt age has risen above 9.0 volt s, normal
transmission oper ation is resu med.
Hardware Error Mode
When the TCM detects a major inter nal error, the
transmission is placed i n th e perma nent Limp-In
Mode an d cea ses all communica tion over the CAN
bus. When th e TCM ha s en tered t his mode normal
transmission operat ion does not r esu me until all
DTCs ar e cleared from th e TCM.
Loss of Drive
If the TCM detect s a situa tion th at h as resulted or
may result in a ca tastr oph ic en gine or tr ansmission
pr oblem, the tr ansmission is placed in the neutral
position . Im proper Rat io, Input Sensor Overspeed or
Engine Over speed DTCs cau se the loss of drive.
Controlled Limp - in Mode
When a fa ilu re does not r equire the TCM to shut
down the solenoid supply, but th e failure is severe
enough tha t the TCM places t he transmission into a
VA ELECTRONIC CONTROL MODULES 8E - 9
To Next Page