POWER TRAIN
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Automatic Transaxle
2-81
TRANSMISSION CONTROL MODULE OUTPUT SIGNALS AND DEVICES
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L
The TCM takes the input information from the
sen-
sembly. The following items are output components
sors, evaluates the input, then uses it to control
operated by the TCM.
the transmission control relay and the solenoid
as-
Transmission Control Relay
Solenoid and pressure
The instant the ignition is turned on, the TCM performs a self-test
to determine if its internal electronic circuits are all working
properly. If the self-test results are good, the TCM sends battery
voltage to the transmission control relay. The relay closes its
internal contacts which then supply battery voltage to the TCM
(confirms function of the relay), the four solenoids and the
three pressure switches in the solenoid assembly. If the TCM
“sees” a problem in the system, it turns off the power feed
to the transmission control relay, causing the contacts to open.
A diagnostic trouble code is then stored in memory. The trans-
mission control relay is located in various places depending
on the vehicle model. It can be located directly on the TCM
or in the harness near the TCM.
Solenoid Assembly
When the transmission control relay contact points are closed,
the solenoid assembly receives electrical power. The TCM
can now operate the solenoids, as determined by its program-
ming. The relay provides power to all four solenoids through
a single wire. This means that all the solenoids have voltage
supplied to them whenever the transmission control relay is
closed. The solenoids, however, are not energized until the
TCM grounds the solenoid return wire for the solenoid that
is needed.
Power and Ground
The ground wire from each solenoid goes back to the TCM.
The TCM energlizes each solenoid by connecting the solenoid
return wire to ground. Four of the wires in the
8-way
solenoid
assembly connector are solenoid return wires. Three wires
are for each pressure switch, and the last wire is the battery
feed wire from the transmission control relay. The TCM controls
both the power feed (through the transmission control relay)
and the ground to each solenoid (through the return wires).
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