• lateral acceleration (calculated by the TCM).
• gear change frequency (how often the shift
occurs).
Based on how aggressive the driver is, the TCM
moves up the shift so that the present gear is held a
little longer before the next upshift. If the driving
style is still aggressive, the shift point is modified up
to ten steps. If the driving returns to normal, then
the shift point modification also returns to the base
position.
This adaptation has no memory. The adaptation to
driving style is nothing more than a shift point mod-
ification meant to assist an aggressive driver. The
shift points are adjusted for the moment and return
to base position as soon as the inputs are controlled
in a more rational manner.
Shift Time Adaptation (Shift Overlap Adaptation, Working
Pressure)
Shift time adaptation is the ability of the TCM to
electronically alter the time it takes to go from one
gear to another. Shift time is defined as the time it
takes to disengage one shift member while another is
being applied. Shift time adaptation is divided into
four categories:
36. Accelerating upshift, which is an upshift under
a load. For shift time adaptation for the 1-2 upshift
to take place, the transmission must shift from 1st to
2nd in six different engine load ranges vs. transmis-
sion output speed ranges.
37. Decelerating upshift, which is an upshift under
no load. This shift is a rolling upshift and is accom-
plished by letting the vehicle roll into the next gear.
38. Accelerating downshift, which is a downshift
under load. This shift can be initiated by the throttle,
with or without kickdown. The shift selector can also
be used.
39. Decelerating downshift, which is accomplished
by coasting down. As the speed of the vehicle
decreases, the transmission downshifts.
Fill Pressure Adaptation (Apply Pressure Adaptation,
Modulating Pressure)
Fill pressure adaptation is the ability of the TCM
to modify the pressure used to engage a shift mem-
ber. The value of this pressure determines how firm
the shift will be.
• If too much pressure is used, the shift will be
hard.
• If too little pressure is used, the transmission
may slip.
The pressure adjustment is needed to compensate
for the tolerances of the shift pressure solenoid valve.
The amount the solenoid valve opens as well as how
quickly the valve can move, has an effect on the pres-
sure. The return spring for the shift member pro-
vides a resistance that must be overcome by the
pressure in order for shift member to apply. These
return springs have slightly different values. This
also affects the application pressure and is compen-
sated for by fill pressure adaptation.
Fill Time Adaptation (Engagement Time Adaptation)
Fill time is the time it takes to fill the piston cav-
ity and take up any clearances for a friction element
(clutch or brake). Fill time adaptation is the ability of
the TCM to modify the time it takes to fill the shift
member by applying a preload pressure.
CONTROLLER MODES OF OPERATION
Permanent Limp-In Mode
When the TCM determines there is a non-recover-
able condition present that does not allow proper
transmission operation, it places the transmission in
permanent Limp-In Mode. When the condition occurs
the TCM turns off all solenoids as well as the sole-
noid supply output circuit. If this occurs while the
vehicle is moving, the transmission remains in the
current gear position until the ignition is turned off
or the shifter is placed in the 9P9 position. When the
shifter has been placed in 9P, 9 the transmission only
allows 2nd gear operation. If this occurs while the
vehicle is not moving, the transmission only allows
operation in 2nd gear.
Temporary Limp-In Mode
This mode is the same as the permanent Limp-In
Mode except if the condition is no longer present, the
system resumes normal operation.
Under Voltage Limp-In Mode
When the TCM detects that system voltage has
dropped below 8.5 volts, it disables voltage-depen-
dant diagnostics and places the transmission in the
temporary Limp-In Mode. When the TCM senses
that the voltage has risen above 9.0 volts, normal
transmission operation is resumed.
Hardware Error Mode
When the TCM detects a major internal error, the
transmission is placed in the permanent Limp-In
Mode and ceases all communication over the CAN
bus. When the TCM has entered this mode normal
transmission operation does not resume until all
DTCs are cleared from the TCM.
Loss of Drive
If the TCM detects a situation that has resulted or
may result in a catastrophic engine or transmission
problem, the transmission is placed in the neutral
position. Improper Ratio, Input Sensor Overspeed or
Engine Overspeed DTCs cause the loss of drive.
WG ELECTRONIC CONTROL MODULES 8Ea - 7
TRANSMISSION CONTROL MODULE (Continued)
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