I have a 2004 WJ with the 4.0, that the PCM has gone bad on due to it getting very full of very muddy water, while having preexisting issues. I'm sure the PCM is the problem, as I was able to get the jeep running again with a PCM out of a 02 WJ 4.0 from the junkyard. My understanding, however, is that due to the wiring changes, notably the control of the engine cooling fan, this isn't really a good solution. @Waterluvr, could you get in touch with me with info on getting a PCM VIN/mileage reprogrammed and SKIM deleted, once a 04 comes into one of my local junkyards? This is a brand new account, so I can't dm. Or, does anyone know of somewhere reliable to get one online so I don't have to wait for one to show up locally? From reading previous posts, it seems like most of the reman ones are untrustworthy, but maybe I just have the wrong impression. Am I correct in my belief that the only donor car I can use is a 2004 6cyl WJ, and no others would be compatible? Thanks everyone!
RedBrassNipples
Here's a post from Waterluvr a while back:
I still help established forum members, but you have to be around here awhile.
Way to much bs with problem child's using low post burner accounts wasting my time. I'm old and in poor health and don't have any more patience for it.
I still help established forum members, but you have to be around here awhile.
Way to much bs with problem child's using low post burner accounts wasting my time. I'm old and in poor health and don't have any more patience for it.
Ah I missed that. Well, does anyone have experience, positive or negative, with ordering a programmed PCM from any of the online vendors like All computer resources, etc? Or do they know of anything other than the 2004 4.0 PCM that would be cross compatible? Can't seem to find a straight answer on wether the 2004 4.7 PCM would work but my experience from mostly subarus is they usually only have programming in them for one engine type. If I can find an ECU that works, does anyone know where I would go for vin/mileage/skim delete programming? Thanks!
Here are some posts by Waterluvr:
If you ever have time look at the BBB rating's for the companies you bought those pcm's from, and do some research here on the forum as well you'll see you are not alone in buying defective products.
Anyone selling ecu's in a Google search or on Ebay is peddling garbage, most of them are using defective cores they buy in large lots from various sources and using hacker methods to try and pair them to work.
Also beware, there are a couple very active auto electronics hackers on this site that create more problems than they solve, and you'll likely hear from one of them after posting this.
Junk automotive electronics sourced from defective cores and then resold with sketchy back door coding methods from internet companies is a multimillion dollar industry in the US with almost zero accountability and you bought into it right along with most people who learn the hard way.
These shady companies are known in the industry to have 60+% failure rates day one out of the box when the part arrives and their business model somehow manages to survive it year after year. Read the BBB feedback from any of the usual suspects that sell them or there's endless threads here about what a low quality experience it is.
There is not one single legitimate source outside dealer service departments and local brick and mortar shops to buy a plug and play pcm / ecu that hasn't already been someone else's problem.
![Image]()
If you ever have time look at the BBB rating's for the companies you bought those pcm's from, and do some research here on the forum as well you'll see you are not alone in buying defective products.
Anyone selling ecu's in a Google search or on Ebay is peddling garbage, most of them are using defective cores they buy in large lots from various sources and using hacker methods to try and pair them to work.
Also beware, there are a couple very active auto electronics hackers on this site that create more problems than they solve, and you'll likely hear from one of them after posting this.
Junk automotive electronics sourced from defective cores and then resold with sketchy back door coding methods from internet companies is a multimillion dollar industry in the US with almost zero accountability and you bought into it right along with most people who learn the hard way.
These shady companies are known in the industry to have 60+% failure rates day one out of the box when the part arrives and their business model somehow manages to survive it year after year. Read the BBB feedback from any of the usual suspects that sell them or there's endless threads here about what a low quality experience it is.
There is not one single legitimate source outside dealer service departments and local brick and mortar shops to buy a plug and play pcm / ecu that hasn't already been someone else's problem.
To answer your question, if you ever check back. A 4.7 PCM of a 04 or any WJ year will not work. There are variables between the 4.7 engines. For instance. The PCM in my 04 Overland will not work in a 04 Limited.
although there are skim issues there were originally only 3 different 2004 WJ PCM according to the parts list
# 56044 563AB ER0 4.0L Engine [DG0]=Automatic Transmission
# 56044 564AB EVA 4.7L Power Tech Engine [DG0]=Automatic Transmission
# 56044 565AB EVC 4.7L Power Tech HO V-8 [DG0]=Automatic Transmission
![Image]()
# 56044 563AB ER0 4.0L Engine [DG0]=Automatic Transmission
# 56044 564AB EVA 4.7L Power Tech Engine [DG0]=Automatic Transmission
# 56044 565AB EVC 4.7L Power Tech HO V-8 [DG0]=Automatic Transmission
Biggest difference between 4.7 and 4.0 (other than the number of cylinders) is that the 4.0 pcm controls BOTH engine and transmission while the functions are split on the 4.7 between different boxes.
IF you could be lucky enough to get the keys from the donor pcm, it’s possible you could be plug and play.
Smart folks can reset the skim if you go donor route.
IF you could be lucky enough to get the keys from the donor pcm, it’s possible you could be plug and play.
Smart folks can reset the skim if you go donor route.
Thanks to everyone for 4.7/4.0 incompatibility confirmation, and to WJ60 for pointing me to that waterluvr post. Some updates if anyone is interested: The often-repeated claim that the SKIM and PCM are permanently linked and no good without each other definitely isn't true, at least in my case. As I mentioned, I got a 2002 PCM and SKIM from the junkyard, and installed both in my 04 with the original lock cylinder. As expected, the truck would start but stall itself due to the key not being programmed. That's when I realized I should try to just program the key, since my scanner (TOPDON ArtiDiag Pro) is supposed to be capable of that.
I went to the local Jeep dealer with my state vehicle registration, state ID, and the junkyard receipt, which had the VIN of the 02. They were more than happy to give me the 4-digit key pin for both VINs, no charge and no hassle. I went to program my old key to the new SKIM, and while it accepted the 4-digit code, I got a communication error during the actual programming. I tried wiping the three keys it said it had in memory and tried again, but same error. I don't know if this is an issue with my setup or a software bug, but I sent a report to TOPDON, so maybe that will provide some clarity, as key programming should be fairly simple. Maybe once a Jeep key has been programmed, it can't be reset to a different immobilizer, but that's definitely not the case with the Subarus I've programmed before.
When digging around in the scanner options to find the key programming, I noticed it also had "special functions" options for PCM replaced, SKIM replaced, and write PCM VIN. I figured I could try those with my original SKIM since it already had the key programmed to it. I installed the original 04 skim with the new 02 PCM and tried the "PCM replaced" function. I figured the 4-digit pin would follow the PCM since it's looked up by VIN in the dealer database, so I entered the 02 pin, and that locked the system out for an hour. Turns out the pin is always tied to the SKIM, not the PCM. After waiting an hour, I tried again. It accepted the 04 pin but had a communication failure during the "transmitting secret key to PCM" phase. Turns out, the PCM VIN needs to match the SKIM to communicate. So, I used the "write VIN" function to reprogram the 02 PCM with the 04 VIN number. Then I tried the "PCM replaced" function again, and it claimed to have finished successfully. I took the key out, put it back in, and the Jeep fired right up, running and driving no problem, with no check engine lights.
I still have the issue that the 02 PCM can't control the cooling fan on the 04, but other than that, this seems like an ideal solution. Would still love to get a SKIM delete at some point so I don't have to deal with chipped keys, but the VINs all match and the car runs so I don't think I have any legal issues. I've read that the PCM can store the mileage, but my scanner doesn't seem to have access to that, and from reading the forum seems like the only thing that can read it is a DRBIII. I think even that can't change it, so I'm not too worried about the potential for a mileage mismatch, someone let me know if I'm missing something I should be concerned about though. I'll keep hoping a local junkyard gets in a 04 4.0 6cyl so I can get the right PCM, but if one hasn't come up by summer when the car might overheat, I'll rig in a switch for the fan. It's a project car I bought for $900 for gambler racing, so it doesn't need to be perfect, far from it.
I went to the local Jeep dealer with my state vehicle registration, state ID, and the junkyard receipt, which had the VIN of the 02. They were more than happy to give me the 4-digit key pin for both VINs, no charge and no hassle. I went to program my old key to the new SKIM, and while it accepted the 4-digit code, I got a communication error during the actual programming. I tried wiping the three keys it said it had in memory and tried again, but same error. I don't know if this is an issue with my setup or a software bug, but I sent a report to TOPDON, so maybe that will provide some clarity, as key programming should be fairly simple. Maybe once a Jeep key has been programmed, it can't be reset to a different immobilizer, but that's definitely not the case with the Subarus I've programmed before.
When digging around in the scanner options to find the key programming, I noticed it also had "special functions" options for PCM replaced, SKIM replaced, and write PCM VIN. I figured I could try those with my original SKIM since it already had the key programmed to it. I installed the original 04 skim with the new 02 PCM and tried the "PCM replaced" function. I figured the 4-digit pin would follow the PCM since it's looked up by VIN in the dealer database, so I entered the 02 pin, and that locked the system out for an hour. Turns out the pin is always tied to the SKIM, not the PCM. After waiting an hour, I tried again. It accepted the 04 pin but had a communication failure during the "transmitting secret key to PCM" phase. Turns out, the PCM VIN needs to match the SKIM to communicate. So, I used the "write VIN" function to reprogram the 02 PCM with the 04 VIN number. Then I tried the "PCM replaced" function again, and it claimed to have finished successfully. I took the key out, put it back in, and the Jeep fired right up, running and driving no problem, with no check engine lights.
I still have the issue that the 02 PCM can't control the cooling fan on the 04, but other than that, this seems like an ideal solution. Would still love to get a SKIM delete at some point so I don't have to deal with chipped keys, but the VINs all match and the car runs so I don't think I have any legal issues. I've read that the PCM can store the mileage, but my scanner doesn't seem to have access to that, and from reading the forum seems like the only thing that can read it is a DRBIII. I think even that can't change it, so I'm not too worried about the potential for a mileage mismatch, someone let me know if I'm missing something I should be concerned about though. I'll keep hoping a local junkyard gets in a 04 4.0 6cyl so I can get the right PCM, but if one hasn't come up by summer when the car might overheat, I'll rig in a switch for the fan. It's a project car I bought for $900 for gambler racing, so it doesn't need to be perfect, far from it.
I suspect that your post of the repair will help a lot of people in the future. Thanks for being specific with the whole thing.
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