Chrysler Dodge Caravan 2002 Manual page 1837

21 - 280 41TE AUTOMATIC TRANSAXLE
SOLENOID/PRESSURE SWITCH ASSY (Continued)
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 by design allow fluid to pass through in their
relaxed or "off" state. 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:
PRESSURE SWITCH STATES
GEAR L/R
R OP
P/N CL
1st CL
2nd OP
D OP
OD OP
OP = OPEN
CL = CLOSED
A Diagnostic Trouble Code (DTC) will set if the
TCM senses any switch open or closed at the wrong
time in a given gear.
2/4 OD
OP OP
OP OP
OP OP
CL OP
OP CL
CL CL
The TCM also tests the 2/4 and OD pressure
switches when they are normally off (OD and 2/4 are
tested in 1st gear, OD in 2nd gear, and 2/4 in 3rd
gear). The test simply verifies that they are opera-
tional, by looking for a closed state when the corre-
sponding element is applied. Immediately after a
shift into 1st, 2nd, or 3rd gear with the engine speed
above 1000 rpm, the TCM momentarily turns on ele-
ment pressure to the 2/4 and/or OD clutch circuits to
identify that the appropriate switch has closed. If it
doesn't close, it is tested again. If the switch fails to
close the second time, the appropriate Diagnostic
Trouble Code (DTC) will set.
REMOVAL
NOTE: If solenoid/pressure switch assembly is
being replaced, it is necessary to perform the TCM
Quick Learn Procedure. (Refer to 8 - ELECTRICAL/
ELECTRONIC CONTROL MODULES/TRANSMISSION
CONTROL MODULE - STANDARD PROCEDURE)
(1) Disconnect battery negative cable.
(2) Remove air cleaner assembly.
(3) Disconnect solenoid/pressure switch assembly
connector.
(4) Disconnect input speed sensor connector.
(5) Remove input speed sensor (Fig. 314).
Fig. 314 Input Speed Sensor
1 - INPUT SPEED SENSOR
RS