Grand Caravan V6-3.3L VIN R (2005)
Pressure Regulating Solenoid: Description and Operation
SOLENOID/PRESSURE SWITCH ASSY
DESCRIPTION
The Solenoid/Pressure Switch Assembly (Fig. 276) is external to the transaxle and mounted to the transaxle case. The assembly consists of four
solenoids that control hydraulic pressure to the LR/CC, 2/4, OD, and UD friction elements. 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 PCM/TCM. Likewise, the pressure
switches can only be service by replacing the assembly.
OPERATION
SOLENOIDS
The solenoids receive electrical power from the Transmission Control Relay through a single wire. The PCM/TCM energizes or operates the solenoids
individually 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 operating state. The result is an apply or release of a frictional 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 PCM/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 pressure switch error occurs.
PRESSURE SWITCHES
The PCM/TCM relies on three pressure switches to monitor fluid pressure in the L/R, 2/4, and OD hydraulic circuits. The primary purpose of these
switches is to help the PCM/TCM detect when clutch circuit hydraulic failures occur. The range for the pressure switch closing 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 PCM/TCM for the correct states (open or closed) in each gear as shown in the
following chart:
