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My brother had his 2004 4.7L Limited diagnosed at the local Jeep dealership as having a bad SKIM. To repair would require a new SKIM and key (they said). The garage did not say if the lock on the steering column would need to be replaced.

I have access to a 2004 4.7 Limited parts jeep that was running till the valve seats dropped. It has a SKIM and the associated keys.
So I guess my questions are:
  1. What else will need to be done if I install the SKIM from the parts jeep? (programming, etc.)
  2. I don't understand the need for a new key - I thought the SKIM could be programmed with the data from the existing key. No?
  3. Since the SKIM communicates to the PCM, does anything need to be reprogrammed on the PCM?

I've never dealt with the details of how these two systems work/cooperate so this is new ground for me. I do have the FSM but the 'theory of operation' is a little thin for my understanding (after all, it is a R&R manual)
If anyone knows of a good doc that describes PCM and SKIM operation, please let me know.
Thanks!
J
 

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When SKIM is installed at the Jeep factory, the Keys with chip are married to the PCM. At the Dealership it is faster, easier, and more profitable to replace everything.

If you have a complete donor, transfer the PCM and the married keys. Naturally you will need to install the donors ignition cylinder as well. Since the key reading device may be the root cause of the problem, swap that as well. While you at it, swap the door and tailgate lock cylinders also.

Failing to keep everything SKIM/SKIS related together as a matched set set will lock up the PCM which requires a tow truck ride to the Dealership for re-programming.


The Sentry Key Immobilizer System (SKIS) system is designed to provide passive protection against unauthorized vehicle use by preventing the engine from operating while the system is armed. The primary components of this system are the Sentry Key Immobilizer Module (SKIM) for sensing the chip-in-key, the Sentry Key transponder keys, the SKIS indicator lamp, and the Powertrain Control Module (PCM). The SKIM is installed on the steering column near the ignition lock cylinder. The transponder chip is located under the molded rubber cap on the head of the ignition key. The SKIS indicator lamp is located in the instrument cluster. The SKIS includes two valid Sentry Key transponders from the factory. If the customer wishes, additional blank Sentry Keys are available. These blank keys can be cut to match a valid ignition key, but the engine will not start unless the key transponder is also programmed to the vehicle using the Customer Learn programming procedure or a DRB-III scan tool. The SKIS will recognize no more than eight valid Sentry Key transponders at any one time.

For diagnosis or initialization (marriage) of the SKIM and the PCM, a DRB-III Scan Tool and the proper Diagnostic Procedures Manual are required. The SKIM cannot be repaired and, if faulty or damaged, the unit must be replaced.
 

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To allow your engine to run the VIN in both the SKIM and PCM must match. The keys are married to the SKIM. There is also a PIN code that is stored in both the PCM and SKIM. This code is used to gain access for key programing and will set code P0633 if mismatched.

Once the keys are programmed to a SKIM they become locked and can not be programed to a different SKIM. The only way to use the same keys on a different SKIM is to clone the eeprom chip from one SKIM to another. This is outside of the scope of a dealership. Also within the realm of the dealership, the SKIM is a one time programable module meaning that once the VIN and PIN are programmed there is no changing them.
 

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I would check for codes, WHAT is the issue.
I often see a communication code and find a broken wire at the SKIM.

SKIS is the system, the KEY has a chip, SKIM is a component a MODULE it reads key - and as the gang mentions all coded.
 

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If you are sure that the problem is in the SKIM module itself and want to replace just that module, then the best way is to go with a NEW skim module.
You need PIN code (comes with a new SKIM), capable scan tool (DRBIII) and two (3,4,5...up to you, but max8) new transponder keys precut to match your
lock cylinder. Then you need to program the SKIM to match the vehicle VIN and program new keys.

If you go with an used one and do not want to swap the lock cylinders and PCM, then you also need a pin code for SKIM from the donor vehicle, scanner and keys.
That way the vehicle VIN programmed into the PCM will not match the one on the body
Same for swapping the entire system.

There are ways how to "virginize" an used SKIM, change VIN, PIN.....You could swap the eeprom from one to another, clone it.....etc etc
but as @Mean_Green_ZJ wrote, its beyond the dealers scope

@jtec - absolutely. Check for codes. SKIM modules do not fail very often. Actually without mechanical damage the fail rate is almost zero.
 

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If you are replacing the SKIM and want the remotes to work, I think you also need to replace the passenger door module which contains the signal receiver and which is programmed to the SKIM.
Others will no doubt know if this is correct?
 
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