Memory Positioning Systems: Description and Operation

POWER SEAT SYSTEM
Power seats can be adjusted in eight directions; up, down, forward, back, tilt forward, or tilt rearward. Four reversible motors and a transmission located on the seat tracks provide the various seat movements.

The electrical circuit is protected by a 40 amp fuse in the Power Distribution Center (PDC) and a 30 amp circuit breaker located in the wire harness under the driver's seat.

MEMORY SEAT AND MIRROR SYSTEM
Memory Seat and Mirror System is available only on Town and Country (Luxury Class) vehicles.

The Memory Seat/Mirror Module (MSMM) is mounted under the driver's seat, on the inboard upper track with Torx head screws. The MSMM provides the driver with an adjustable seat, recliner, and power side view mirror positioning control that remembers stored positions and will recall those positions on command.

The MSMM reads all seat and recliner switch inputs and operates the seat and recliner motors in response to switch actuation. The MSMM monitors position sensing potentiometers (mounted on the motors) for seat and recliner positioning.

Soft stops are set each time the track is physically stalled (i.e. an obstruction in the seat's path). This is used by the MSMM to not run the motor into a stall condition on subsequent movement. However, this can unduly restrict the seat's range of travel if the stall was due to something other than the true end of travel.

The MSMM operates the power side view mirror motors through solid state drivers (electronic switches) in the recall mode only, and follows the glass face position by means of rheostats built into the motor pack assembly of the mirrors. Normal electrical operation of the mirrors is accomplished by actuation of the power mirror switch.

The MSMM monitors the memory switches and has the capability to store desired positions in nonvolatile memory in response to a valid input sequence. Refer to Memory Selector Switches (1, 2, and S) and Remote Keyless Entry (RKE) Data Link. The memory seat/mirror module also can activate the previously described motors in response to a recall request from an individual memory switch.

The MSMM monitors a data link from the BCM and will respond to stored information or modify stored information when requested by a valid data stream.

The MSMM is connected to the system through a seat wiring harness that interfaces with all of the components within the seat structure, and with electrical distribution wiring harness connections to the non-seat mounted components. The module operates the seat and recliner motors through relays: four dedicated to track forward/rearward, track front up/down, track rear up/down, and recliner forward/ rearward. A fifth relay controls the direction of operation of those motors.

POSITION SENSING SEAT AND RECLINER POTENTIOMETERS
A potentiometer is mounted to each seat track and recliner motor end-bell to provide a sense voltage to the MSMM that will indicate to the module where the seat track or recliner is positioned.

This sense voltage is derived from a 5 volt source provided by the MSMM to the potentiometer. The sense voltage is input into the module and stored by the MSMM.

SEAT AND RECLINER SWITCHES
The seat and recliner switch assembly is mounted outboard on the seat side-shield. Press and hold the desired seat or recliner switch to effect movement.

The Memory Seat/Mirror Module (MSMM) will drive a maximum of 2 motors at a time in a given direction. If conflicting directions are requested, the priority for response will be as follows:
- Seat Track Rearward
- Seat Front Down
- Seat Rear Down
- Recliner Rearward
- Seat Track Forward
- Seat Front Up
- Seat Rear Up
- Recliner Forward

The inputs from these switches to the MSMM is a current limited battery source fed by the MSMM. This protects the MSMM printed circuit board traces from acting as fuses. All of these switch contact inputs to the MSMM are normally closed to ground, except when actuated.

Soft stops are incorporated to prevent the motor from being driven into a stall. Should the seat have restricted travel, refer to Resetting Soft Stops.