Jeep 200 Cherokee, Service Manual

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The Sentry Key transponder is within the range of
the SKIM transceiver antenna ring when it is inserted
in the ignition lock cylinder. When the ignition switch is
turned to the Start or On positions, the SKIM trans-
ceiver issues a Radio Frequency (RF) signal that excites
the transponder chip. The transponder chip responds by
issuing an RF signal containing its transponder identi-
fication code and the “Secret Key” code. The SKIM
transceiver compares the transponder codes with the
codes stored in its memory to determine whether a valid
key is in the ignition lock cylinder.
The Sentry Key transponder cannot be repaired
and, if faulty or damaged, it must be replaced.
SENTRY KEY IMMOBILIZER SYSTEM
INDICATOR LAMP
The Sentry Key Immobilizer System (SKIS) indica-
tor lamp gives an indication when the SKIS is faulty
or when the vehicle has been immobilized due to the
use of an invalid ignition key. The lamp is controlled
by the instrument cluster circuitry based upon mes-
sages received from the Sentry Key Immobilizer
Module (SKIM) on the Chrysler Collision Detection
(CCD) data bus.
The SKIM sends messages to the instrument clus-
ter to turn the lamp on for about three seconds when
the ignition switch is turned to the On position as a
bulb test. After completion of the bulb test, the SKIM
sends bus messages to keep the lamp off for a dura-
tion of about one second. Then the SKIM sends mes-
sages to the instrument cluster circuitry to turn the
lamp on or off based upon the results of the SKIS
self-tests. If the SKIS indicator lamp comes on and
stays on after the bulb test, it indicates that the
SKIM has detected a system malfunction and/or that
the SKIS has become inoperative.
If the SKIM detects an invalid key when the ignition
switch is turned to the On position, it sends messages to
the instrument cluster to flash the SKIS indicator lamp.
The SKIM can also send messages to the instrument
cluster to flash the lamp and to generate a single audi-
ble chime tone. These functions serve as an indication
to the customer that the SKIS has been placed in its
“Customer Learn” programming mode. See Sentry Key
Immobilizer System Transponder Programming in this
group for more information on the “Customer Learn”
programming mode.
The SKIS indicator lamp uses a replaceable incan-
descent bulb and bulb holder on the instrument clus-
ter electronic circuit board. Refer to Group 8E -
Instrument Panel Systems for diagnosis and service
of a faulty SKIS indicator lamp. If the SKIS indicator
lamp comes on and stays on after the bulb test func-
tion, diagnosis of the SKIS should be performed with
a DRB scan tool and the proper Diagnostic Proce-
dures manual.
DIAGNOSIS AND TESTING
SENTRY KEY IMMOBILIZER SYSTEM
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS,
REFER TO GROUP 8M - PASSIVE RESTRAINT SYS-
TEMS BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, OR INSTRUMENT PANEL COM-
PONENT DIAGNOSIS OR SERVICE. FAILURE TO TAKE
THE PROPER PRECAUTIONS COULD RESULT IN
ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
NOTE: The following tests may not prove conclu-
sive in the diagnosis of this system. The most reli-
able, efficient, and accurate means to diagnose the
Sentry Key Immobilizer System involves the use of
a DRB scan tool. Refer to the proper Diagnostic
Procedures manual for the procedures.
The Sentry Key Immobilizer System (SKIS) and
the Chrysler Collision Detection (CCD) data bus net-
work should be diagnosed using a DRB scan tool.
The DRB will allow confirmation that the CCD data
bus is functional, that the Sentry Key Immobilizer
Module (SKIM) is placing the proper messages on the
CCD data bus, and that the Powertrain Control Mod-
ule (PCM) and the instrument cluster are receiving
the CCD data bus messages. Refer to the proper
Diagnostic Procedures manual for the procedures.
Refer to 8W-39 - Vehicle Theft Security System in
Group 8W - Wiring Diagrams for complete circuit
descriptions and diagrams.
(1) Check the fuses in the fuseblock module. If OK,
go to Step 2. If not OK, repair the shorted circuit or
component as required and replace the faulty fuse.
(2) Disconnect and isolate the battery negative
cable. Unplug the wire harness connector at the
SKIM. Check for continuity between the ground cir-
cuit cavity of the SKIM wire harness connector and a
good ground. There should be continuity. If OK, go to
Step 3. If not OK, repair the open circuit to ground
as required.
(3) Connect the battery negative cable. Check for
battery voltage at the fused B(+) circuit cavity of the
SKIM wire harness connector. If OK, go to Step 4. If
not OK, repair the open circuit to the fuse in the
fuseblock module as required.
(4) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run/start) circuit cavity of the SKIM wire
harness connector. If OK, use a DRB scan tool and
the proper Diagnostic Procedures manual to complete
the diagnosis of the SKIS. If not OK, repair the open
circuit to the fuse in the fuseblock module as
required.
XJ
VEHICLE THEFT/SECURITY SYSTEMS 8Q - 3
DESCRIPTION AND OPERATION (Continued)