PCM Compatibility Question - JeepForum.com
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post #1 of 15 Old 07-09-2020, 12:39 PM Thread Starter
YyZed
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PCM Compatibility Question

I have a 1999 Grand Cherokee 4.7 with California emissions. The part number of my PCM is 56041428AI. The question I have is which PCMs are compatible with my Jeep. From reading the forums it appears that the last 3 digits of the part number are the important ones. When looking for PCMs at the junk yard, should I only be looking for a 1999 model year Jeep 4.7 w/California emissions, or will any 428 series PCM be able to be flashed to my Jeep?

For reference, when looking up a Mopar rebuilt PCM compatible with 56041428AI, they list R6044428AJ as the part number for the rebuild, but also list 56041428AC; 56041428AD; 56041428AE; 56041428AF; 56041428AH; 56041428AI; 56041428AJ; 56041428AK; 56044428AB; 56044428AC; 56044428AD; 56044428AE; 56044428AG; 56044428AH; 56044428AI; 56044428AJ as compatible units.

I was hoping that if I found any of the about part number above, they could be flashed to my Jeep?

Any clarification would be appreciated.

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post #2 of 15 Old 07-09-2020, 01:43 PM
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The last two letters indicate the "Revision" number. In the case of the PCM it's usually an indicator of the programming level.

A 56044428AJ PCM will work with any of the older revisions and any older revision can be flashed with the latest programming.

So if you find any of the ones you've listed in your second paragraph you'll be good.
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post #3 of 15 Old 07-09-2020, 03:08 PM Thread Starter
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Thanks a lot for the info.
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post #4 of 15 Old 07-11-2020, 07:19 AM
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Originally Posted by JeepRonibo View Post
A 56044428AJ PCM will work with any of the older revisions and any older revision can be flashed with the latest programming.
In terms of obtaining the final firmware release for a particular PCM series, is that readily available with a TechAuthority subscription?

Their "Preview TechAuthority On-line" thing doesn't work properly, so it's hard to tell:

https://techauthorityonlinedemo.extr...horityDemo.jsp

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post #5 of 15 Old 07-11-2020, 01:39 PM
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Guys, just for the sake of having a better experience when replacing a pcm your way ahead of the curve sticking to the exact part number that was in your Jeep. The last two letters in the suffix don't much matter but the part numbers need to match or your getting into a complete data dump and reflash versus a far less evasive driver update.

I flash piles of these every week and pcm crashing / bricking is a real problem with these older modules if your trying to jerk one over with a completely different flash revision and there are differences in many of the hardware builds that aren't compatible on critical driver circuits.
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post #6 of 15 Old 07-11-2020, 03:22 PM
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Originally Posted by Waterluvr View Post
Guys, just for the sake of having a better experience when replacing a pcm your way ahead of the curve sticking to the exact part number that was in your Jeep. The last two letters in the suffix don't much matter but the part numbers need to match or your getting into a complete data dump and reflash versus a far less evasive driver update.

I flash piles of these every week and pcm crashing / bricking is a real problem with these older modules if your trying to jerk one over with a completely different flash revision and there are differences in many of the hardware builds that aren't compatible on critical driver circuits.
Waterluvr - say I get lucky and find a 56041637AA or 56041637AB at the salvage yard tomorrow from another 2000 WJ (mine is 56041637AC); is it a simple matter of pulling the 56041637AG firmware from TechAuthority to bring any of these 56041637* PCMs up to the final firmware release for the 56041637 series?

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post #7 of 15 Old 07-11-2020, 07:43 PM
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Originally Posted by AustinLonghorn View Post
Waterluvr - say I get lucky and find a 56041637AA or 56041637AB at the salvage yard tomorrow from another 2000 WJ (mine is 56041637AC); is it a simple matter of pulling the 56041637AG firmware from TechAuthority to bring any of these 56041637* PCMs up to the final firmware release for the 56041637 series?
I take it you've never flashed a pcm prior to now? There's nothing simple about the process, you need to build a bench programming harness, have the right power supply and a modern scanner with a pass through device and laptop etc.

Don't even try using anything old school like a handheld Miller Tools device I can about guarantee you'll brick the module doing an update these days via Tech Authority on the vehicle.

That 20 year old wiring harness in the Jeep had data transfer issues the day it left the factory, 20 years later it hasn't improved.

Just grab what you need off of https://www.car-part.com/ they usually have piles of them, I can flash it for you.

If you have any questions send me a PM with your email be glad to help you.
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post #8 of 15 Old 07-12-2020, 07:49 AM
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Originally Posted by Waterluvr View Post
I take it you've never flashed a pcm prior to now? There's nothing simple about the process, you need to build a bench programming harness, have the right power supply and a modern scanner with a pass through device and laptop etc.
No, but I'm kind of interested in doing it as a project (the salvage yard PCMs are $20 a piece, so it's low risk). Still not entirely sure the PCM is the issue on my WJ, either. If I find an '00 PCM, I'll take the three harness connectors this time with the PCM to build a cable. I have a 12-14V adjustable 70A supply for flashing, and access to a DRBIII emulator.

I'll no doubt be PM'ing you, but probably when I actually have an expensive Mopar remanufactured PCM in-hand that warrants a more experienced approach.

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post #9 of 15 Old 07-12-2020, 09:11 AM
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Quote:
Originally Posted by AustinLonghorn View Post
No, but I'm kind of interested in doing it as a project (the salvage yard PCMs are $20 a piece, so it's low risk). Still not entirely sure the PCM is the issue on my WJ, either. If I find an '00 PCM, I'll take the three harness connectors this time with the PCM to build a cable. I have a 12-14V adjustable 70A supply for flashing, and access to a DRBIII emulator.

I'll no doubt be PM'ing you, but probably when I actually have an expensive Mopar remanufactured PCM in-hand that warrants a more experienced approach.
Let me save you some $$$. Those Mopar *expensive* pcm's? They get those under contract from yards out of running wrecks, then they blast the cabinet to clean them up and put a fancy orange re-manufactured sticker on it and throw your wallet a beating.

ZERO difference from anything you get out of the yard for $20.00 outside of general appearance.
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post #10 of 15 Old 07-12-2020, 03:03 PM
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Originally Posted by Waterluvr View Post
Let me save you some $$$. Those Mopar *expensive* pcm's? They get those under contract from yards out of running wrecks, then they blast the cabinet to clean them up and put a fancy orange re-manufactured sticker on it and throw your wallet a beating.

ZERO difference from anything you get out of the yard for $20.00 outside of general appearance.
Good to know, thanks.

I got lucky and found a P56041637AF at the salvage yard today (only one 2000 WJ left at the moment; the other two '00 WJs apparently went off to the crusher yesterday ).

I also cut off the harness/pigtails on the donor vehicle and made a bench harness; didn't need the fancy flash power supply and just used a server PSU. Alligator clip is the ignition switch, purple lead is unused alternator output. I fired it up first with the '04 ECU just to make sure everything was wired up properly per the FSM pinouts.

I was able to easily flash this junk yard PCM up to P56041637AG with a Tech Authority download, but how the devil do you reset the VIN, enter the SKIM PIN, etc., on the bench?
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post #11 of 15 Old 07-13-2020, 06:09 AM
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How? You blow the dust off your wallet and buy an Autel MaxiSys Elite to handle that.

Or just pop that in the Mail and I'll take care of it for you. ~That will save you several thousand dollars.
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post #12 of 15 Old 07-13-2020, 06:24 AM
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^^^ +1.....postage is much cheaper than the Autel!
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post #13 of 15 Old 07-13-2020, 07:50 AM
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^^^ +1.....postage is much cheaper than the Autel!
The Snap-On scanner will handle that also, it's another couple grand more and has about 50% of the functionality of the Autel Elite with some heavy handed annual software pirate tactics that come with it.

I have one collecting dust. The Autel's are nice, they are the best tool in the business and you don't have to go broke buying updates for them every year if you don't need them.

Not many of us that run independent shops work on late model vehicles still under warranty, no need for updates every year about every 5 years is all we need.
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post #14 of 15 Old 07-13-2020, 10:50 AM
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SUCCESS!

The junk yard PCM is installed, has the correct VIN and is cooperating with the SKIM module; I was looking in the wrong menu section (it's all under anti-theft / SKIM / PCM replacement, yeesh).

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post #15 of 15 Old 07-13-2020, 04:07 PM
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Nice job !!
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