Grand Cherokee 4WD V8-4.7L VIN N (2000)
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.
Memory Seat Glide (If Equipped)
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 (R). When using
the DRBIII (R) 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 (R) 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.
Part 3 of 3
SENTRY KEY IMMOBILIZER SYSTEM (SKIS)
The Sentry Key Immobilizer System (SKIS) is an immobilizer system designed to prevent unauthorized vehicle operation. The system consists of
a Sentry Key Immobilizer Module (SKIM), ignition key(s) equipped with a transponder chip and engine controller. When the ignition switch is
turned ON, the SKIM interrogates the ignition key. If the ignition key is "Valid" the SKIM sends a PCI Bus message to the engine controller
indicating the presence of a valid ignition key. Upon receiving a "Valid" key signal the PCM will allow the engine to continue to operate.
SKIS Operation
When ignition power is supplied to the SKIM, the SKIM performs an internal self-test. After the self-test is completed, the SKIM energizes the
antenna (this activates the transponder chip) and sends a challenge to the transponder chip. The transponder chip responds to the challenge by
generating an encrypted response message using the following:
Secret Key - This an electronically stored value (identification number) that is unique to each SKIS. The secret key is stored in the SKIM, PCM
and all ignition key transponders.
Challenge - This is a random number that is generated by the SKIM at each ignition key cycle.
