Description And Operation; Memory Seat Module; Power Lumbar Switch; Power Recliner Adjuster And Motor - Jeep 1997 Grand Cherokee Service Manual

8R - 2 POWER SEAT SYSTEMS

DESCRIPTION AND OPERATION

MEMORY SEAT MODULE

A Memory Seat Module (MSM), mounted under the
inboard side of the driver side front seat cushion, is
used on this model to control all of the driver side
power seat memory functions and features. The MSM
contains a central processing unit and interfaces with
other modules in the vehicle on the Chrysler Colli-
sion Detection (CCD) data bus network.
The MSM receives hard-wired inputs from the
power seat switch, the power lumbar switch, and the
potentiometers on each of the driver side power seat
motors. The MSM receives messages on the CCD
data bus from the Driver Door Module (DDM) (mem-
ory set/select switch status), the Powertrain Control
Module (PCM) (vehicle speed status), and the Body
Control Module (seat belt switch status). The pro-
gramming in the MSM allows it to process the infor-
mation from these inputs and send control outputs to
each of the driver side power seat motors. The MSM
will prevent the seat memory function from being ini-
tiated if the driver side seat belt is buckled, or if the
vehicle is moving.
For diagnosis of the MSM or the CCD data bus,
refer to the proper Body Diagnostic Procedures man-
ual. The MSM cannot be repaired and, if faulty, it
must be replaced.

POWER SEAT SWITCH

The power seat can be adjusted in eight different
ways using the power seat switch. The switch is
located at the lower outboard side of the seat cushion
on the seat cushion side shield. Refer to the owner's
manual for more information on the power seat
switch functions and the seat adjusting procedures.
The individual switches in the power seat switch
module cannot be repaired. If one switch is damaged
or faulty, the entire power seat switch module must
be replaced.

POWER LUMBAR SWITCH

The power lumbar adjuster on each front seat can
be moved in or out electrically by operating the sin-
gle two-way switch mounted near the front of the
outboard seat cushion side shield.
The power lumbar switches cannot be repaired
and, if faulty or damaged, they must be replaced.

POWER SEAT ADJUSTER AND MOTORS

There are three reversible motors that operate the
power seat adjuster. The motors are connected to
worm-drive gearboxes that move the seat adjuster
through a combination of screw-type drive units.
The front and rear of a seat are operated by differ-
ent motors. They can be raised or lowered indepen-
dently of each other. When the seat switch is pushed
to the Up or Down position, both the front and rear
motors operate in unison, moving the entire seat up
or down. The forward-rearward motor is operated by
pushing the seat switch to its forward or rearward
position.
When a switch is actuated, a battery feed and a
ground path are applied through the switch contacts
to the motor(s). The motor(s) operate to move the
seat in the selected direction until the switch is
released, or until the travel limit of the power seat
adjuster is reached. When the switch is moved in the
opposite direction, the battery feed and ground paths
to the motor(s) are reversed through the switch con-
tacts. This causes the motor to run in the opposite
direction.
Each motor contains a self-resetting circuit breaker
to protect it from overload. Consecutive or frequent
resetting of the circuit breakers must not be allowed
to continue, or the motors may be damaged. Make
the necessary repairs. The motors used on models
with the optional memory system also have a posi-
tion potentiometer included in the motor assembly.
The power seat adjuster and motors cannot be
repaired, and are serviced only as a complete unit. If
any component in this unit is faulty or damaged, the
entire power seat adjuster and motors assembly must
be replaced.

POWER RECLINER ADJUSTER AND MOTOR

The power recliner adjuster uses a reversible motor
to operate the seat back recliner adjuster. The motor
is connected to a gearbox that moves the recliner
adjuster through a screw-type drive unit.
When the power recliner switch is actuated, a bat-
tery feed and a ground path are applied through the
switch contacts to the motor. The motor operates to
move the seat back in the selected direction until the
switch is released, or until the travel limit of the
power recliner adjuster is reached. When the switch
is moved in the opposite direction, the battery feed
and ground paths to the motor are reversed through
the switch contacts. This causes the motor to run in
the opposite direction.
The motor contains a self-resetting circuit breaker
to protect it from overload. Consecutive or frequent
resetting of the circuit breaker must not be allowed
to continue, or the motor may be damaged. Make the
necessary repairs. The motor used on models with
the optional memory system also has a position
potentiometer included in the motor assembly.
The power recliner adjuster and motor cannot be
repaired, and is serviced only as a complete unit. If
any component in this unit is faulty or damaged, the
entire power recliner adjuster and motor assembly
must be replaced.
ZG