2002 JEEP GRAND CHEROKEE Alarm module

The ITM microprocessor continuously monitors
inputs from its on-board motion sensor as well as
inputs from the BCM and the alarm siren module.
The ITM motion sensor transmits ultrasonic signals
into the vehicle cabin through a transmit transducer,
then listens to the returning signals as the bounce off
of objects in the vehicle interior. If an object is mov-
ing in the interior, a detection circuit in the ITM
senses this movement through the modulation of the
returning ultrasonic signals that occurs due to the
Doppler effect. The motion detect function of the ITM
can be disabled by depressing the ªLockº button on
the Remote Keyless Entry (RKE) transmitter three
times within fifteen seconds, while the security indi-
cator is still flashing rapidly or by cycling the key in
the driver door cylinder from the center to the lock
position. The ITM will signal the alarm siren module
to provide a single siren ªchirpº as an audible confir-
mation that the motion sensor function has been dis-
abled.
If movement is detected, the ITM sends an mes-
sage to the BCM over the PCI data bus to flash the
exterior lighting and send a message to the alarm
siren module over a dedicated serial bus line to
sound the siren. When the BCM detects a breach in
the perimeter protection through a door, tailgate,
flip-up glass, or hood ajar switch input, it sends an
message to the ITM and the ITM sends an message
to the BCM over the PCI data bus to flash the exte-
rior lighting and send a message to the alarm siren
module over a dedicated serial bus line to sound the
siren. The ITM also monitors inputs from the alarm
siren module for siren battery or siren input/output
circuit tamper alerts, and siren battery condition
alerts, then sets active and stored Diagnostic Trouble
Codes (DTC) for any monitored system faults it
detects. An active fault only remains for the current
ignition switch cycle, while a stored fault causes a
DTC to be stored in memory by the ITM. If a fault
does not reoccur for fifty ignition cycles, the ITM will
automatically erase the stored DTC.
The ITM is connected to the vehicle electrical sys-
tem through the overhead wire harness. The ITM
receives battery voltage on a B(+) circuit through a
fuse in the Junction Block (JB), and is grounded to
the chassis at G303. These connections allow the
ITM to remain operational, regardless of the ignition
switch position. The hard wired inputs and outputs
for the ITM may be diagnosed and tested using con-
ventional diagnostic tools and procedures. However,
conventional diagnostic methods will not prove con-
clusive in the diagnosis of the ITM, the PCI data bus
network, or the electronic message inputs to and out-
puts from the ITM. The most reliable, efficient, and
accurate means to diagnose the ITM, the PCI data
bus network, and the message inputs to and outputsfrom the ITM requires the use of a DRBIIItscan
tool. Refer to the appropriate diagnostic information.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) While pulling downward lightly on the rear cor-
ner of the Intrusion Transceiver Module (ITM) trim
cover, insert a small thin-bladed screwdriver through
each of the service holes on the rear edge of the trim
cover to release the two integral rear latch features
of the module from the mounting bracket above the
headliner (Fig. 7).
(3) Pull the ITM trim cover rearward far enough
to disengage the two front latch features of the mod-
ule from the mounting bracket above the headliner.
(4) Pull the ITM and trim cover down from the
headliner far enough to access and disconnect the
overhead wire harness connector for the ITM from
the module connector.
(5) Remove the ITM from the headliner.
INSTALLATION
(1) Position the Intrusion Transceiver Module
(ITM) to the headliner.
(2) Reconnect the overhead wire harness connector
for the ITM to the module connector.
(3) Align the two front latch features of the ITM
with the two front latch receptacles of the mounting
bracket above the headliner (Fig. 8).
(4) Push the ITM trim cover forward far enough to
insert the two rear latch features of the module into
Fig. 7 INTRUSION TRANSCEIVER MODULE
REMOVE
1 - SMALL SCREWDRIVER
2 - HEADLINER
3 - SERVICE HOLES
4 - ITM
8Q - 12 VEHICLE THEFT SECURITYWJ
INTRUSION TRANSCEIVER MODULE (Continued)

the two rear latch receptacles of the mounting
bracket above the headliner.
(5) Push upward firmly and evenly on the rear
edge of the ITM trim cover until the two rear latch
features of the module are engaged and latched in
the mounting bracket above the headliner.
(6) Reconnect the battery negative cable.
NOTE: If the Intrusion Transceiver Module (ITM) has
been replaced with a new unit, the new ITM MUST
be initialized before the Vehicle Theft Security Sys-
tem can operate as designed. The use of a DRBIIIT
scan tool is required to initialize the ITM. Refer to
the appropriate diagnostic information.
SIREN
DESCRIPTION
An alarm siren module is part of the premium ver-
sion of the Vehicle Theft Alarm (VTA) in the Vehicle
Theft Security System (VTSS) (Fig. 9). The premium
version of the VTA is only available in vehicles built
for certain markets, where the additional features
offered by this system are required. The alarm siren
module is located in the right front frame rail. This
unit is designed to provide the audible alert require-
ments for the premium VTA.
The alarm siren module consists of microprocessor,
the siren, and a nickel metal hydride backup battery.
All of the alarm module components are protected
and sealed within the housing.The alarm siren module cannot be repaired or
adjusted and, if faulty or damaged, it must be
replaced.
OPERATION
The microprocessor within the alarm siren module
provides the siren unit features and functions based
upon internal programming and arm and disarm
messages received from the Intrusion Transceiver
Module (ITM) over a dedicated serial bus communi-
cation circuit. The alarm siren module will self-detect
problems with its internal and external power supply
and communication circuits, then send messages
indicating the problem to the ITM upon receiving a
request from the ITM. The ITM will store a Diagnos-
tic Trouble Code (DTC) for a detected alarm siren
module fault that can be retrieved with the DRBIIIt
scan tool over the Programmable Communications
Interface (PCI) data bus.
When the premium version of the Vehicle Theft
Alarm (VTA) is armed, the alarm siren module con-
tinuously monitors inputs from the ITM for messages
to sound its siren and enters its auto-detect mode.
While in the auto-detect mode, if the alarm siren
module detects that its power supply or communica-
tion circuits are being tampered with or have been
sabotaged, it will sound an alarm and continue to
operate through its on-board backup battery. If the
arm siren module is in its disarmed mode when its
power supply or communication circuits are inter-
rupted, the siren will not sound. The alarm module
will also notify the ITM when the backup battery
requires charging, and the ITM will send a message
that will allow the backup battery to be charged
through the battery voltage and ground circuits to
the alarm module only when the ignition switch is in
the On position and the engine is running. This will
prevent the charging of the alarm backup battery
from depleting the charge in the main vehicle battery
while the vehicle is not being operated.
The alarm siren module receives battery voltage
through a fuse in the Power Distribution Center
(PDC), and is grounded to the chassis. These connec-
tions allow the alarm siren module to remain opera-
tional, regardless of the ignition switch position. The
hard wired inputs and outputs for the alarm siren
module may be diagnosed and tested using conven-
tional diagnostic tools and procedures. However, con-
ventional diagnostic methods will not prove
conclusive in the diagnosis of the internal circuitry or
the backup battery of the alarm siren module, the
ITM, the serial bus communication line, or the mes-
sage inputs to and outputs from the alarm siren
module. The most reliable, efficient, and accurate
means to diagnose the alarm siren module, the ITM,
the serial bus communication line, and the electronic
Fig. 8 INTRUSION TRANSCEIVER MODULE
RETAINER RING
1 - STAMPED NUT (2)
2 - MOUNTING BRACKET
3 - HEADLINER
4 - LATCH RECEPTACLES (4)
WJVEHICLE THEFT SECURITY 8Q - 13
INTRUSION TRANSCEIVER MODULE (Continued)

message inputs to and outputs from the alarm siren
module requires the use of a DRBIIItscan tool.
Refer to the appropriate diagnostic information.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Disconnect the alarm siren module wiring har-
ness connector. (Fig. 9).
(3) Remove the screws that secure the alarm siren
module to the left frame rail.
(4) Remove the alarm siren module.
INSTALLATION
(1) Position the alarm siren module on to the left
frame rail. (Fig. 9).
(2) Install and tighten the screws that secure the
alarm siren moduleto the frame rail. Tighten the
screws to 6 N´m (50 in. lbs.).
(3) Reconnect the alarm siren module wiring har-
ness connector.
(4) Reconnect the battery negative cable.
NOTE: If the alarm siren module has been replaced
with a new unit, the new unit MUST be configured
in the Intrusion Transceiver Module (ITM) before the
Vehicle Theft Security System can operate as
designed. The use of a DRBIIITscan tool is requiredto configure the alarm siren module settings in the
ITM. Refer to the appropriate diagnostic informa-
tion.
SKIS INDICATOR LAMP
DESCRIPTION
A Sentry Key Immobilizer System (SKIS) indicator
lamp is standard equipment on all instrument clus-
ters, but is only functional on vehicles equipped with
the optional SKIS. The amber SKIS indicator lamp is
located to the right of the oil pressure gauge.
OPERATION
The Sentry Key Immobilizer System (SKIS) indica-
tor lamp gives an indication to the vehicle operator of
the status of the SKIS. This lamp is controlled by a
transistor on the instrument cluster circuit board
based upon messages received by the cluster from
the Sentry Key Immobilizer Module (SKIM) over the
Programmable Communications Interface (PCI) data
bus. The SKIS indicator lamp bulb receives battery
current on the instrument cluster circuit board
through the fused ignition switch output (st-run) cir-
cuit whenever the ignition switch is in the On or
Start positions. The lamp bulb only illuminates when
it is provided a path to ground by the instrument
cluster transistor. The instrument cluster will turn
on the SKIS indicator lamp for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position, the SKIM tells the cluster
to illuminate the lamp for about three seconds.
²SKIS Lamp-On Message- Each time the clus-
ter receives a SKIS lamp-on message from the SKIM,
the lamp will be illuminated. The lamp can be
flashed on and off, or illuminated solid, as dictated
by the message from the SKIM. For more informa-
tion on the SKIS and the SKIS lamp control param-
eters, (Refer to 8 - ELECTRICAL/VEHICLE THEFT
SECURITY - OPERATION - SENTRY KEY IMMO-
BILIZER SYSTEM). The lamp remains illuminated
until the cluster receives a lamp-off message from
the SKIM or until the ignition switch is turned to the
Off position, whichever occurs first.
²Actuator Test- Each time the cluster is put
through the actuator test, the lamp will be turned on
for the duration of the test to confirm the functional-
ity of the lamp and the cluster.
The SKIM performs a self-test each time the igni-
tion switch is turned to the On position to decide
whether the system is in good operating condition.
The SKIM then sends a message to the instrument
cluster. If the SKIS indicator lamp fails to light dur-
ing the bulb test, replace the bulb. For further diag-
nosis of the SKIS indicator lamp or the instrument
Fig. 9 Siren Remove/Install
1 - SIREN
2 - FRAME
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SIREN (Continued)