Caravan V6-201 3.3L (1995)
Control Module: Description and Operation
Electronic Transmission Controller Operation
LOCATION
The EATX control module is located under the hood, in a potted, die cast aluminum housing with a sealed, 60-way connector.
ADAPTIVE CONTROLS
These controls function by reading the input and output speeds over 140 times a second and responding to each new reading.
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This provides the precise friction element control needed to make smooth clutch-to-clutch shifts for all gear changes.
As with most automatic transaxles, all shifts involve releasing one element and applying a different element.
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In simplified terms, the upshift logic allows the releasing element to slip backwards slightly, to ensure that it does not have excess capacity; the
apply element is filled until it begins to make the speed change to the higher gear; its apply pressure is then controlled to maintain the desired
rate of speed change until the shift is complete.
The key to providing excellent shift quality is precision;
EXAMPLE As mentioned, the release element for upshifts is allowed to slip backwards slightly; the amount of that slip is typically less than a
total of 20 degrees.
LEARNING
To achieve that precision, the EATX control module learns the characteristics of the particular transaxle that it is controlling.
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It learns the release rate of the releasing element and the apply time of the applying element.
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It also learns the rate at which the apply element builds pressure sufficient to begin making the speed change.
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This method achieves more precision than would be possible with exacting tolerances. It can also adapt to any changes that occur with age or
environment, for example, altitude, temperature, engine output, etc.
KICKDOWN SHIFTING
For kickdown shifts, the control logic allows the releasing element to slip and then controls the rate at which the input (and engine) accelerate;
when the lower gear speed is achieved, the releasing element reapplies to maintain that speed until the apply element is filled.
This provides quick response since the engine begins to accelerate immediately and a smooth torque exchange since the release element can
control the rate of torque increase.
This control can make any power train feel more responsive without increasing harshness.
SUMMARY
Adaptive controls respond to input speed changes They compensate for changes in engine or friction element torque and provide good, consistent
shift quality for the life of the transaxle.
