Grand Cherokee 4WD V8-4.7L (2003)
(MSM), the PCI radio. They will in turn position the driver seat, driver side view mirror and set the radio presets. When the RKE button is pressed,
depending on which transmitter (# 1 or # 2), the passenger door module sends the recall message.
POWER SEAT
The memory power seat provides the driver with 2 position settings for the driver's seat. Each power seat motor is connected to the MSM with two
circuits. Each circuit is switched between battery and ground. By alternating the circuits the MSM controls the movement of the motors based on input
from the seat mounted switch.
Each motor contains a potentiometer to monitor the seat position. To monitor the position of the motor, the MSM sends out a 5 volt reference on the
sensor supply circuit. The sensor is grounded back to the module on a common ground circuit. Based on the position of the sensor, the MSM monitors
the voltage change through the sensor on a separate signal circuit.
The MSM stores the input value of each of the four seat potentiometers in memory when the system is requested. The driver can initiate memory
recall, using either the memory switch or the RKE transmitter. When initiated, the MSM adjusts the four seat motors to match the memorized seat
position data.
For safety reasons, the memory seat recall is disabled by the MSM when the vehicle is out of park position or if the seatbelt is buckled. Any
obstruction to seat movement over a 2 second delay will cause the seat to stop moving in which case a stalled motor would be detected by the MSM
which would then flag a trouble code and the corresponding seat output would be deactivated. However, if the object obstructing the seat is removed,
the seat will function normally again.
EASY EXIT SEAT (AVAILABLE WITH MEMORY SEAT)
The intent of this feature is to allow for easier entry and exit to the vehicle by moving the seat rearward a short distance when the operator turns the
vehicle off. The seat can be recalled to one of it's two set memory positions by pressing either of the memory recall buttons on the switch or the RKE
transmitters. If any seat movement is initiated, whether manual or by memory recall, after the ignition has been turned off, this will cancel any ensuing
glide to enter movement until the next ignition cycle.
This feature can be enabled/disabled by the owner through the electronic vehicle information center (EVIC) or using the DRBIII. When using the
DRBIII it will also inform as to what state it is in. To reinstate the feature, simply repeat the process.
GUARD BANDS
The module provides guard bands which prevent the seat track from hitting the hard limits of the given seat axis during manual power seat operation.
The guard band values for each hard limit are stored in EEPROM. The guard band can be bypassed by running the seat to the end of its travel and then
releasing the switch and pressing it again. The seat will move a short distance further. Once the seat is past the guard band, it can be stored in memory,
but if recall is initiated the seat will move to the guard bands and no further.
When a seat module or seat track assembly is replaced, the DRBIII must be used to perform the "Reset Guard Bands" procedure. WARNING: The
operator must be out of the seat when this procedure is being used as the seat will move to the end of it's travel in all 8 positions.
ELECTRICALLY HEATED SEATS
The heated seat feature is available with or without the memory system. The module is located under the driver's seat and is known as the heated seat
module (HSM) or the memory heated seat module (MHSM). The control switches for the heated seats are located on the instrument panel and are
wired to the body control module. The BCM then sends the message to the HSM via the PCI bus. The system offers two seat temperature settings of
approximately 96.8 °F (36 °C) (LO) and approximately 107.6 °F (41 °C) (HI).
As the temperature in the seat rises, the negative temperature coefficient (NTC) resistance decreases and the voltage reading detected by the HSM
decreases. The seat heater output is deactivated once the voltage reading reaches it's threshold for either setting, high or low.
As the temperature decreases, the voltage reading increases until the upper threshold is reached for either setting high or low. At this point the seat
heat output is activated once again and this cycle repeats itself as long as the seat heat request is on. The thresholds for low and high settings are
preprogrammed into the module memory
The heated seat switch contain resistors pulled up to 5 volts which are processed by the body control module as the voltage readings indicating desired
heat setting high or low.
The heater elements inside the seat back and cushion are different for the Limited and Laredo models. The Laredo seat heater elements are wired in
series whereas the Limited seat elements are wired in parallel. This means that if an element is open in a Laredo model there will be no heater output
to either the cushion or the seat back. If an element is open in a Limited model, the other elements will operate as usual. However, if one of the
elements is open, the seat cushion will have to be replaced.
There are three heater elements in the seat cushions for both models. The Laredo uses a resistor wire for its center and both side bolsters (raised outer
side panels) and the Limited uses a carbon fiber element for its center and resistor wire for the bolsters.
Power Sunroof
POWER SUNROOF
The power sunroof in the Grand Cherokee is controlled by the Body Control Module (BCM). After the ignition has been turned off, the power sunroof
