SOLENOID/PRESSURE SWITCH ASSEMBLY
DESCRIPTION
The Solenoid/Pressure Switch Assembly (Fig. 17) is
inside the transaxle and mounted to the valve body
assembly. The assembly consists of four solenoids
that control hydraulic pressure to the L/R, 2/4, OD,
and UD friction elements (transaxle clutches), and
the torque converter clutch. The reverse clutch is
controlled by line pressure from the manual valve in
the valve body. The solenoids are contained within
the Solenoid/Pressure Switch Assembly, and can only
be serviced by replacing the assembly.
The solenoid assembly also contains pressure
switches that monitor and send hydraulic circuit
information to the TCM. Likewise, the pressure
switches can only be service by replacing the assem-
bly.
OPERATION
SOLENOIDS
The solenoids receive electrical power from the
Transmission Control Relay through a single wire.
The TCM energizes or operates the solenoids individ-
ually by grounding the return wire of the solenoid
needed. When a solenoid is energized, the solenoid
valve shifts, and a fluid passage is opened or closed
(vented or applied), depending on its default operat-
ing state. The result is an apply or release of a fric-
tional element.
The 2/4 and UD solenoids are normally applied,
which allows fluid to pass through in their relaxed or
“off” state. By design, this allows transaxle limp-in
(P,R,N,2) in the event of an electrical failure.
The continuity of the solenoids and circuits are
periodically tested. Each solenoid is turned on or off
depending on its current state. An inductive spike
should be detected by the TCM during this test. It no
spike is detected, the circuit is tested again to verify
the failure. In addition to the periodic testing, the
solenoid circuits are tested if a speed ratio or pres-
sure switch error occurs.
PRESSURE SWITCHES
The TCM relies on three pressure switches to mon-
itor fluid pressure in the L/R, 2/4, and OD hydraulic
circuits. The primary purpose of these switches is to
help the TCM detect when clutch circuit hydraulic
failures occur. The range for the pressure switch clos-
ing and opening points is 11-23 psi. Typically the
switch opening point will be approximately one psi
lower than the closing point. For example, a switch
may close at 18 psi and open at 17 psi. The switches
are continuously monitored by the TCM for the cor-
rect states (open or closed) in each gear as shown in
the following chart:
A Diagnostic Trouble Code (DTC) will set if the
TCM senses any switch open or closed at the wrong
time in a given gear.
Fig. 16 Transmission Control Relay Location
(Typical)
1 – TRANSMISSION CONTROL RELAY
2 – PDC
3 – TCM
Fig. 17 Solenoid/Pressure Switch Assembly
1 – SOLENOID/PRESSURE SWITCH
2 – TRS
3 – TRANSFER PLATE
4 – SEPARATOR PLATE
5 – VALVE BODY
21 - 14 42LE TRANSAXLE LH
DESCRIPTION AND OPERATION (Continued)
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