Dodge Dakota 2001, Service Manual

Page: 331 / 2307

SKIM is connected to the vehicle electrical system
through a single take out and connector of the
instrument panel wire harness.
The SKIM cannot be adjusted or repaired. If faulty
or damaged, the entire SKIM unit must be replaced.
OPERATION
The Sentry Key Immobilizer Module (SKIM) con-
tains a Radio Frequency (RF) transceiver and a
microprocessor. The SKIM transmits RF signals to,
and receives RF signals from the Sentry Key tran-
sponder through a tuned antenna enclosed within the
molded plastic antenna ring integral to the SKIM
housing. If this antenna ring is not mounted properly
around the ignition lock cylinder housing, communi-
cation problems between the SKIM and the transpon-
der may arise. These communication problems will
result in Sentry Key transponder-related faults. The
SKIM also communicates over the Programmable
Communications Interface (PCI) data bus with the
Powertrain
Control Module (PCM), the Central
Timer Module (CTM), and/or the DRBIII
t
scan tool.
The SKIM retains in memory the ID numbers of
any Sentry Key transponder that is programmed into
it. A maximum of eight Sentry Key transponders can
be programmed into the SKIM. For added system
security, each SKIM is programmed with a unique
Secret Key code. This code is stored in memory, sent
over the PCI data bus to the PCM, and is encoded to
the transponder of every Sentry Key that is pro-
grammed into the SKIM. Therefore, the Secret Key
code is a common element that is found in every com-
ponent of the Sentry Key Immobilizer System (SKIS).
Another security code, called a PIN, is used to gain
access to the SKIM Secured Access Mode. The
Secured Access Mode is required during service to
perform the SKIS initialization and Sentry Key tran-
sponder programming procedures. The SKIM also
stores the Vehicle Identification Number (VIN) in its
memory, which it learns through a PCI data bus
message from the PCM during SKIS initialization.
In the event that a SKIM replacement is required,
the Secret Key code can be transferred to the new
SKIM from the PCM using the DRBIII
t
scan tool
and the SKIS initialization procedure. Proper com-
pletion of the SKIS initialization will allow the exist-
ing Sentry Keys to be programmed into the new
SKIM so that new keys will not be required. In the
event that the original Secret Key code cannot be
recovered, SKIM replacement will also require new
Sentry Keys. The DRBIII
t
scan tool will alert the
technician during the SKIS initialization procedure if
new Sentry Keys are required.
When the ignition switch is turned to the On posi-
tion, the SKIM transmits an RF signal to the tran-
sponder in the ignition key. The SKIM then waits for
an RF signal response from the transponder. If the
response received identifies the key as valid, the
SKIM sends a valid key message to the PCM over
the PCI data bus. If the response received identifies
the key as invalid, or if no response is received from
the key transponder, the SKIM sends an invalid key
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 an invalid key; therefore, if
no message is received from the SKIM by the PCM,
the engine will be disabled and the vehicle immobi-
lized after two seconds of running.
The SKIM also sends security indicator status
messages to the CTM over the PCI data bus to tell
the CTM how to operate the security indicator. The
CTM then controls the security indicator in the Elec-
troMechanical Instrument Cluster (EMIC) through a
hard wired security indicator driver circuit. The secu-
rity indicator status message from the SKIM tells the
CTM to turn the indicator on for about three seconds
each time the ignition switch is turned to the On
position as a bulb test. After completion of the bulb
test, the SKIM sends security indicator status mes-
sages to the CTM to turn the indicator off, turn the
indicator on, or to flash the indicator on and off. If
the security indicator flashes or stays on solid after
the bulb test, it signifies a SKIS fault. If the SKIM
detects a system malfunction and/or the SKIS has
become inoperative, the security indicator will stay
on solid. If the SKIM detects an invalid key or if a
key transponder-related fault exists, the security
indicator will flash. If the vehicle is equipped with
the Customer Learn transponder programming fea-
Fig. 10 Sentry Key Immobilizer Module
1 - SENTRY KEY IMMOBILIZER MODULE
2 - IGNITION LOCK CYLINDER HOUSING
3 - SCREW
4 - INSTRUMENT PANEL WIRE HARNESS CONNECTOR
8E - 16 ELECTRONIC CONTROL MODULES
AN
SENTRY KEY IMMOBILIZER MODULE (Continued)