Chrysler 300M Service Manual page 263

LH
SENTRY KEY IMMOBILIZER MODULE (Continued)
Fig. 11 SENTRY KEY IMMOBILIZER MODULE
LOCATION
1 - STEERING WHEEL
2 - IGNITION KEY CYLINDER
3 - STEERING COLUMN
4 - SENTRY KEY IMMOBILIZER MODULE
The SKIM and the PCM both use software that
includes a rolling code algorithm strategy, which
helps to reduce the possibility of unauthorized SKIS
disarming. The rolling code algorithm ensures secu-
rity by preventing an override of the SKIS through
the unauthorized substitution of the SKIM or the
PCM. However, the use of this strategy also means
that replacement of either the SKIM or the PCM
units will require a system initialization procedure to
restore system operation.
When the ignition switch is turned to the ON or
START positions, the SKIM transmits an RF signal
to excite the Sentry Key transponder. The SKIM then
listens for a return RF signal from the transponder
of the Sentry Key that is inserted in the ignition lock
cylinder. If the SKIM receives an RF signal with
valid "Secret Key" and transponder identification
codes, the SKIM sends a "valid key" message to the
PCM over the PCI bus. If the SKIM receives an
invalid RF signal or no response, it sends "invalid
key" messages to the PCM. The PCM will enable or
disable engine operation based upon the status of the
SKIM messages.
The SKIM also sends messages to the BCM which
controls the VTSS indicator LED. The SKIM sends
messages to the BCM to turn the LED 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 LED off for a duration of about one second. Then
the SKIM sends messages to turn the LED on or off
based upon the results of the SKIS self-tests. If the
VTSS indicator LED comes on and stays on after the
bulb test, it indicates that the SKIM has detected a
ELECTRONIC CONTROL MODULES 8E - 15
system malfunction and/or that the SKIS has become
inoperative.
If the SKIM detects an invalid key when the igni-
tion switch is turned to the ON position, it sends
messages to flash the VTSS indicator LED. The
SKIM can also send messages to flash the LED and
to generate a single audible chime tone. These func-
tions serve as an indication to the customer that the
SKIS has been placed in its "Customer Learn" pro-
gramming mode. See Sentry Key Immobilizer System
Transponder Programming in this section for more
information on the "Customer Learn" programming
mode.
For diagnosis or initialization of the SKIM and the
PCM, a DRB III scan tool and the proper Body
Diagnostic Procedures Manual are required. The
SKIM cannot be repaired and, if faulty or damaged,
the unit must be replaced.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO ELECTRICAL, RESTRAINTS,
WARNINGS, BEFORE ATTEMPTING COMPONENT
DIAGNOSIS OR SERVICE. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
(1) Open hood and disconnect the negative battery
cable remote terminal from the remote battery post
(Fig. 12).
Fig. 12 NEGATIVE BATTERY CABLE REMOTE
TERMINAL
1 - RIGHT STRUT TOWER
2 - AIR CLEANER INLET TUBE
3 - REMOTE TERMINAL
(2) Remove knee blocker.