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Old 04-23-2011, 03:33 PM
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Sentry key keeps loosing programming:

2001 WJ 4L 138k NP242

Backstory:
Purchased a 2001 WJ that had been a in a collision with a fence or tree. When the auction house received the vehicle it had no keys. A sentry key was mechanically cut and then included with the vehicle.

When I got the vehicle the transmission shift cable had popped off, so the vehicle was stuck in drive and therefore would not crank. After reconnecting the shift cable the vehicle cranked and started normally. With the exception that the engine would only run for 3 seconds at a time like the sentry key was not programmed.

I had assumed that the key was never programmed to the vehicle because the shift cable was popped off, and since it didn't crank there was no reason to program the sentry key to the vehicle.

Thursday I finally called a locksmith out, he programmed the key that came with the vehicle. I started and ran the vehicle several times and for an extended period on thursday.

Friday morning when the windshield guy came I was unable to start the vehicle normally. The vehicle started then died after 3 seconds, and then displayed the sentry key light. I called up the locksmith again and he came out and cut a new sentry key, then programmed it. The newly cut and programmed key worked correctly. Additionally the other key that was programmed the previous day then worked correctly.

This morning I started the vehicle only to have it die 3 seconds later.




So does anyone have any thoughts for me?




This is my next train of thought, which I am not completely certain of, as I have to profess my ignorance of these systems since I have not had to deal with them yet.

So I have some problem with the sentry key system. As far as I know there are three components to the system.

The RF antenna ring/PCI data bus interface which sits around the tumbler(believe this is called the SKIM).

The BCM.

The ECU.

From my understand of the KJ system(which may not be correct but its the best I can figure out). The RF reader sends the code to the BCM, and then the BCM sends an "OK" signal to the ECU. Once the ECU has the sentry key recognition circuit/software activated it cannot be deactivated.

This is similar to the XJ system but a little different, the XJ has no BCM so the RF antenna transmits the signal directly to the ECU via the CCD bus. Being that the WJ predates the KJ by 3 years I'm wondering if the WJ is not a little more like the XJ, and the RF antenna unit(SKIM) transmits directly to the ECU.

Anyways what all that means is that I think there are three possible things that could be wrong in the system, the SKIM unit, the BCM, or the ECU.

Any thoughts for me?
(Forgive me if any of that did not make sense, I am suffering from a pretty bad head cold so I am having a hard time thinking straight.)
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Old 04-23-2011, 04:11 PM
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Re: Sentry key keeps loosing programming:

My initial thinking is that the SKIM itself is bad. And reading this blurb would seem to confirm that:

Quote:
OPERATION
The Sentry Key Immobilizer Module (SKIM) contains
a Radio Frequency (RF) transceiver and a
microprocessor. The SKIM transmits RF signals to,
and receives RF signals from the Sentry Key tran-
Fig. 14 Powertrain Control Module (PCM) Mounting
Bracket
1 - PCM BRACKET
2 - PCM
3 - PCM-TO-BRACKET SCREWS (3)
Fig. 15 Sentry Key Immobilizer Module
1 - STEERING COLUMN
2 - SKIM
3 - MOUNTING SCREW
WJ ELECTRONIC CONTROL MODULES 8E - 17
POWERTRAIN CONTROL MODULE (Continued)
sponder through a tuned antenna ring integral to the
SKIM housing. If this antenna ring is not mounted
properly around the ignition lock cylinder housing,
communication problems between the SKIM and the
transponder 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 ElectroMechanical
Instrument Cluster (EMIC), the Body
Control Module (BCM), and/or the DRBIIIt scan tool.
The SKIM retains in memory the ID numbers of
any Sentry Key transponder that is programmed into
it. A maximum of eight 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 programmed into
the SKIM. 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 transponder 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 DRBIIIt scan tool
and the SKIS replacement procedure. Proper completion
of the SKIS initialization will allow the existing
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 DRBIIIt scan tool will alert the technician
during the SKIS replacement procedure if new Sentry
Keys are required.
When the ignition switch is turned to the On position,
the SKIM transmits an RF signal to the transponder
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 immobilized
after two seconds of running.
The SKIM also sends indicator light status messages
to the EMIC over the PCI data bus to tell the
EMIC how to operate the SKIS indicator. This indicator
light status message tells the EMIC 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 indicator light status messages to the EMIC to
turn the indicator off, turn the indicator on, or to
flash the indicator on and off. If the SKIS indicator
lamp 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 SKIS indicator will stay on solid. If the SKIM
detects an invalid key or if a key transponder-related
fault exists, the SKIS indicator will flash. If the vehicle
is equipped with the Customer Learn transponder
programming feature, the SKIM will also send messages
to the EMIC to flash the SKIS indicator lamp,
and to the BCM to generate a single audible chime
tone whenever the Customer Learn programming
mode is being utilized. (Refer to 8 - ELECTRICAL/
VEHICLE THEFT SECURITY - STANDARD PROCEDURE
- SENTRY KEY TRANSPONDER
PROGRAMMING).
The SKIS performs a self-test each time the ignition
switch is turned to the On position, and will
store fault information in the form of Diagnostic
Trouble Codes (DTC’s) in SKIM memory if a system
malfunction is detected. The SKIM can be diagnosed,
and any stored DTC’s can be retrieved using a
DRBIIIt scan tool. Refer to the appropriate diagnostic
information.
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Old 04-23-2011, 04:25 PM
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Re: Sentry key keeps loosing programming:

If you have a DRBIII scan tool, you can try to read fault codes stored in the SKIM. The SKIM keeps the ID number of the sentry keys in its memory. Connected to the SKIM is the antenna ring, which is mounted around the ignition cylinder. Did you check if the antenna ring is at its right place? The collision impact of the car could have dislocated it from its proper position.
The signal goes from the SKIM via de PCI bus to the PCM. As far as i understood has the BCM nothing to do with the valid/unvalid signal from the SKIM. There is a signal going to the BCM, but that is used to generate an audible chime. (no idea when this chime will work)
Is the sentry key light steady on or is it flashing? Steady on means a system malfunction, while a flashing light means an invalid key or transponder problem.
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Old 04-23-2011, 05:15 PM
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Re: Sentry key keeps loosing programming:

Quote:
Originally Posted by Frango100 View Post
If you have a DRBIII scan tool, you can try to read fault codes stored in the SKIM. The SKIM keeps the ID number of the sentry keys in its memory. Connected to the SKIM is the antenna ring, which is mounted around the ignition cylinder. Did you check if the antenna ring is at its right place? The collision impact of the car could have dislocated it from its proper position.
The signal goes from the SKIM via de PCI bus to the PCM. As far as i understood has the BCM nothing to do with the valid/unvalid signal from the SKIM. There is a signal going to the BCM, but that is used to generate an audible chime. (no idea when this chime will work)
Is the sentry key light steady on or is it flashing? Steady on means a system malfunction, while a flashing light means an invalid key or transponder problem.
Alas I wish I had a $2000-3000 to spend on the DRBIII. I have been watching but have been unable to find any I can afford. That rules out programming my own keys(hence the call to a locksmith) and retrieving any SKIM error codes.

Once I get to feeling a bit better I will inspect the antenna ring, however I highly doubt that is the problem, as that would seem to indicate a problem all the time, and not an intermittent state where it works shortly after programming.

No light indication until after engine shutoff, at which time it is lit continuously.

Sounds more and more like I am in for a SKIM replacement.
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Old 04-23-2011, 05:41 PM
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Re: Sentry key keeps loosing programming:

It should be at least not the key. Did you try to reset it by disconnecting the battery? Otherwise seems to be the SKIM as you had stated as well.
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Old 04-23-2011, 09:41 PM
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Re: Sentry key keeps loosing programming:

Quote:
Originally Posted by Frango100 View Post
It should be at least not the key. Did you try to reset it by disconnecting the battery? Otherwise seems to be the SKIM as you had stated as well.
Yes I have tried disconnecting the batt cable to "reset" everything.

No the key does not appear to be the problem as I had hoped, seems like its most likely the SKIM at this point.

Man I really wish I had a DRBIII now, I started looking for one when I knew I was going to need to do the key, found couple for reasonable prices(read $500) but missed out on because someone beat me to em.

So if it is the SKIM then I'm gonna have to take it to a dealer for that repair, which involves a tow and finding a dealer with a reasonible rate, I have an account with a dealer about an hour away, but would need to figure out how to get it to them.

@#$@#$@ sentry key system, I wish there was a way to disable it.
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Old 04-23-2011, 10:42 PM
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Re: Sentry key keeps loosing programming:

Is there any way to find a SKIM on the junkyard with a key?
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Old 04-23-2011, 11:13 PM
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Re: Sentry key keeps loosing programming:

Quote:
Originally Posted by Frango100 View Post
Is there any way to find a SKIM on the junkyard with a key?
I could find a used SKIM easily, with key, less easily.

Also, it is my understanding that you need both the SKIM, key and ECU together in order to replace a SKIS system.

If I had a DRBIII this would have been easy, with the DRBIII I could take a used SKIM, read the "secret code" (which is different from the SKIM PIN). And program the new SKIM very easily.

And of course its going to be nearly impossible to find a 99 without the sentry system to replace the ECU with.
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Old 04-23-2011, 11:14 PM
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Re: Sentry key keeps loosing programming:

Oh, and now there is no sentry light illuminated at all.(as if operation was normal, and there was no transponder key in place, only a mechanical key).

Next up is to pull the column cover and play around with the RF antenna/SKIM.
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Old 04-25-2011, 06:46 AM
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Re: Sentry key keeps loosing programming:

This seems like an appropriate place to ask this question I've always had. Not trying to thread jack, maybe an answer could help in your problem.

My Jeep came with an aftermarket remote start system. If I start the Jeep with the remote, I still have to put a key into the ignition, turn it to the on position, and then shift out of drive (there's a safety on the brake so if there's no key and the brake is pushed it dies). But the key that's used in the ignition does NOT have to have a chip in it. I have a regular old key from Lowes that I use.

Does anyone know how remote start systems are able to over ride the system and allow it to start?
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Old 04-25-2011, 11:45 AM
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Re: Sentry key keeps loosing programming:

Quote:
Originally Posted by JeepMe View Post
Does anyone know how remote start systems are able to over ride the system and allow it to start?
Basically they contain a transponder and antenna. You can wrap the antenna around the SKIM halo to simulate the existence of the sentry key.

Or a transponder key can be placed in the halo the SKIM left connnected to the system, but not the key tumbler.
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Old 05-08-2011, 10:28 AM
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Re: Sentry key keeps loosing programming:

Well problem solved, ended up deleting the SKIM system! Yay! No more SKIM keys needed! I still have the two transponder keys that I cut, and one non transponder, but they all work now like they are supposed to without the SKIM system.

If I ever come across this problem in the future I think I am just going to delete the SKIM system rather than try to work with it. It costs about the same to delete the SKIM system as get a new cut programmed.
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