Chrysler Pacifica CS 2004, Руководство по обслуживанию, Страница: 16 / 370

PCI Bus message, or coded messages to the
SKREEM. If all of the criteria for monitoring a
circuit or function are met and a fault is sensed, a
diagnostic trouble code will be stored in the
SKREEM memory.
3.2.8 SKREES OPERATION
When ignition power is supplied to the SKREEM,
the SKREEM performs an internal self-test. After
the self-test is completed, the SKREEM energizes
the antenna (this activates the transponder chip)
and sends a challenge to the transponder chip. The
transponder chip responds to the challenge by gen-
erating an encrypted response message using the
following:
Secret Key - This is an electronically stored
value (identification number) that is unique to each
SKREES. The secret key is stored in the SKREEM,
PCM and all ignition key transponders.
Challenge - This is a random number that is
generated by the SKREEM at each ignition key
cycle.
The secret key and challenge are the two vari-
ables used in the algorithm that produces the
encrypted response message. The transponder uses
the crypto algorithm to receive, decode and respond
to the message sent by the SKREEM. After re-
sponding to the coded message, the transponder
sends a transponder I.D. message to the SKREEM.
The SKREEM compares the transponder I.D. to the
available valid key codes in the SKREEM memory
(8 key maximum at any one time). After validating
the key ignition the SKREEM sends a PCI Bus
message called a Seed Request to the engine con-
troller then waits for a PCM response. If the PCM
does not respond, the SKREEM will send the seed
request again. After three failed attempts the
SKREEM will stop sending the seed request and
store a trouble code. If the PCM sends a seed
response, the SKREEM sends a valid/invalid key
message to the PCM. This is an encrypted message
that is generated using the following:
VIN - Vehicle Identification Number
Seed - This is a random number that is generated
by the PCM at each ignition key cycle.
The VIN and seed are the two variables used in
the rolling code algorithm that encrypts the valid/
invalid key message. The PCM uses the rolling code
algorithm to receive, decode and respond to the
valid/invalid key message sent by the SKREEM.
After sending the valid/invalid key message the
SKREEM waits 3.5 seconds for a PCM status mes-
sage from the PCM. If the PCM does not respond
with a valid key message to the SKREEM, a fault is
detected and a trouble code is stored.
The SKREES incorporates a VTSS LED located
on the instrument panel upper cover. The LED
receives switched ignition voltage and is hardwired
to the body control module. The LED is actuated
when the SKREEM sends a PCI Bus message to the
body controller requesting the LED on. The body
controller then provides the ground for the LED.
The SKREEM will request VTSS LED operation for
the following:
– bulb checks at ignition on
– to alert the vehicle operator to a SKIS mal-
function
– customer key programming mode
For all faults except transponder faults and VTSS
LED remains on steady. In the event of a transpon-
der fault the LED flashes at a rate of 1 Hz (once per
second). If a fault is present the LED will remain on
or flashing for the complete ignition cycle. If a fault
is stored in SKREEM memory which prevents the
system from operating properly, the PCM will allow
the engine to start and run (for 2 seconds) up to six
times. After the sixth attempt, the PCM disables
the starter relay until the fault is corrected.
3.2.9 PROGRAMMING THE POWERTRAIN
CONTROL MODULE
Important Note: Before replacing the PCM for a
failed driver, control circuit or ground circuit, be
sure to check the related component/circuit integ-
rity for failures not detected due to a double fault in
the circuit. Most PCM driver/control circuit failures
are caused by internal failure to components (i.e.
12-volt pull-ups, drivers and ground sensors). These
failures are difficult to detect when a double fault
has occurred and only one DTC has set.
NOTE: If the PCM and the SKREEM are
replaced at the same time, program the VIN
into the PCM first. All vehicle keys will then
need to be replaced and programmed to the
new SKREEM.
The SKREES Secret Key is an I.D. code that is
unique to each SKREES. This code is programmed
and stored in the SKREEM, engine controller and
transponder chip (ignition key). When replacing the
PCM it is necessary to program the secret key into
the PCM.
NOTE: After replacing the PCM, you must
reprogram pinion factor.
1. Turn the ignition on (transmission in park/
neutral).
2. Use the DRBIII
t
and select THEFT ALARM,
SKREEM then MISCELLANEOUS.
3. Select PCM REPLACED.
4. Enter secured access mode by entering the vehi-
cle four-digit PIN.
10
GENERAL INFORMATION