Chrysler PT Cruiser. Manual - part 475
work with the vehicle. The
9Secret Key9 code is there-
fore a common element found in all components of
the Sentry Key Immobilizer System (SKIS). In the
event that a SKIM replacement is required, the
9Secret Key9 code can be restored from the PCM by
following the SKIM replacement procedure found in
the DRB III
t scan tool. Proper completion of this
task will allow the existing ignition keys to be repro-
grammed. Therefore, new keys will NOT be needed.
In the event that the original
9Secret Key9 code can
not be recovered, new ignition keys will be required.
The DRB III
t scan tool will alert the technician if
key replacement is necessary. Another security code,
called a PIN, is used to gain secured access to the
SKIM for service. The SKIM also stores in its mem-
ory the Vehicle Identification Number (VIN), which it
learns through a bus message from the PCM during
initialization. The SKIS scrambles the information
that is communicated between its components in
order to reduce the possibility of unauthorized SKIM
access and/or disabling.
OPERATION
When the ignition switch is moved to the RUN
position, the SKIM transmits an RF signal to the
transponder in the ignition key. The SKIM then
waits for a response RF signal from the transponder
in the key. If the response received identifies the key
as valid, the SKIM sends a
9valid key9 message to
the PCM over the PCI bus. If the response received
identifies the key as invalid or no response is
received from the transponder in the ignition key, the
SKIM sends an
9invalid key9 message to the PCM.
The PCM will enable or disable engine operation
based upon the status of the SKIM messages. It is
important to note that the default condition in the
PCM is
9invalid key.9 Therefore, if no response is
received by the PCM, the engine will be immobilized
after two (2) seconds of running.
The SKIM also sends indicator light status mes-
sages to the instrument cluster to tell that module
how to operate the light. This may consist of turning
the light ON for a three (3) second bulb test when
the ignition switch is first turned to the ON position.
It is also the method used to turn the light ON solid
or to flash it after the indicator light test is complete
to signify a fault in the SKIS. If the light comes ON
and stays ON solid after the indicator light test, this
signifies that the SKIM has detected a system mal-
function and/or that the SKIS has become inopera-
tive. If the SKIM detects an invalid key OR a key-
related fault exists, the indicator light will flash
following the indicator light test. The SKIM may also
request an audible chime if the customer key pro-
gramming feature is available and the procedure is
being utilized. Refer to Electrical, Vehicle Theft Secu-
rity, Transponder Key, Standard Procedure - Sentry
Key Immobilizer System Transponder programming.
STANDARD PROCEDURE - SENTRY KEY
IMMOBILIZER SYSTEM INITIALIZATION
The Sentry Key Immobilizer System (SKIS) initial-
ization should be performed following a Sentry Key
Immobilizer Module (SKIM) replacement. It can be
summarized as follows:
(1) Obtain the vehicle’s unique four-digit PIN
assigned to its original SKIM from the vehicle owner,
Fig. 24 SENTRY KEY IMMOBILIZER MODULE
Fig. 25 SENTRY KEY IMMOBILIZER MODULE
LOCATION
1 - STEERING COLUMN
2 - SKIM ELECTRICAL CONNECTOR
3 - SKIM
8E - 16
ELECTRONIC CONTROL MODULES
PT
SENTRY KEY IMMOBILIZER MODULE (Continued)