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AW4 to AX15 swap ECU / TCU question

well i forgot the camera, left it at home and I'm at my parents house now. will post pics in about 2-2 1/2 hrs.
 
Alright here's some pics I took with my dad's camera. I brought the PCM along to show to my friend and compare with the units in his 96 and 98 XJs. Notice the quality construction and use of a holesaw (? what? why??) Looks like this thing was opened with a masonry chisel and a 4 lb sledge. And a hole saw. The first unit I got from them was beautiful. This thing is a disaster. This doesn't show any comparison with my OEM PCM which the other pictures do but maybe it'll help.

pcm1.jpg


pcm2.jpg


pcm3.jpg


pcm4.jpg


pcm5.jpg


pcm6.jpg
 
Well that computer looks nothing like a 96 or a 98 computer. Which I would venture to say that rules it out as being an OBDII XJ computer. So what is it? ZJ? WJ? Caravan? It's gotta be a chrysler product. My friend took a stab that it might be a 2000 Grand Cherokee 5 speed (auto) computer. I am still getting 3 codes on the scanner, which I did not write down. P14 something which was manufacturer specific and I didn't look up, 7 something I believe which was TPS related and P1698 which is the same freakin no TCU Bus code I was getting before. Which heightens my suspicions that it is STILL a PCM for an auto tranny.
 
Its not a ZJ or WJ PCM, they are both different, even the plugs. Your original PCM number goes with a 2000 XJ w/4.0L cali emissions and auto transmission. The one you have now is listed as the same except the transmission. I took a look at the wiring diagrams and there is nothing in PCM pin out that would cause the problem you have. In fact the pinout is the same between the manual and auto PCM. I don't know what you did with the NSS, but even if you mucked that up I don't see how it would give you this problem.

The part number is correct. Maybe there is an issue with the wiring of the NSS, which you said you bypassed(which I seriously doubt is the issue). More likely what you have is a hacked up pos PCM.

http://www.jeepforum.com/forum/f11/best-correct-method-reset-ecm-548305/ about the third post down are the steps to reset the PCM. Try that first, but given the issue with the efan its a long shot.
 
Alright I will give that a shot. Also wanted to just try swapping it in again to see if I coulda done something stupid wrong. I'm sure nothing I did with the NSS is causing this. It runs fine with the oem PCM and all I did was hook up a switch so it is in "park" to start and "drive" while driving.
 
I don't see how you could have done something stupid. Especially with the backfire and fan issue. Long shot, but what color is the head of your key? It is a possibility that the sentry key is stopping it from running (if you have one), but it usually doesn't cause it to back fire and the efan to turn on. Usually it allows it to start fine and run for a few seconds then cuts off with a flashing no key sign on the dash.
 
The key is black and it is pretty thin. I believe my moms wj has the sentry key and it is a lot thicker and gray.
 
I tried everything suggested this morning, on both the original and the new PCMs. Started up fine with the old PCM, I got the e-fan again on the new PCM and about 5 seconds of crank and then a backfire. The "no buS" thing came on the dash after about 10-30 seconds but it displayed the mileage before that came up. The three codes I read from it are:

P1491 - Seems to be related to fan control circuit.
P0505 - Idle Control System
P1698pd - not sure why the lower case "pd" was after it, but that was the same code I get with the original PCM about "no bus communication with TCU"

I think I did get a "hacked up POS PCM" as you said Talyn. There should be nothing going on with the e-fan. And I should NOT still be getting a P1698 code! I think my plan for the day is to call a bunch of different yards and put in a request on carpart.com to see if I can get the correct PCM at least and make sure that corrects my original problem. If it does then I can get that unit reflashed with my VIN.
 
Since your key is black and thin you do not have the sentry key bs.

You can also check ebay. The important part is that you need a 56041668A PCM. The last number indicates the revision, but I wouldn't go any earlier than G. Also important is that if it is a used PCM make sure that the donor vehicle did not have sentry key. I don't think many XJs had that so you should be safe, but check.
 
I would like to find out what AutoComputerExchange will do as far as return/refund. I am pretty sure this is the right unit, but I am totally sure the one they sent me is messed up. I found a place thru car-part.com in NY that says they have one that is an H. How do you tell if it has sentry key, you just have to ask? Also, whatever I buy, I have to have someone program in my jeep's VIN right?
 
Also, because you say it is cali emissions, I assume it is "Low Emissions" not "Federal"?
 
low emissions = cali emissions. Federal is the one you don't want.

muddygp said:
How do you tell if it has sentry key, you just have to ask? Also, whatever I buy, I have to have someone program in my jeep's VIN right?
Click to expand...


You have to ask. If they don't know you need to get the VIN of the donor vehicle and call a Jeep dealer and ask them.. i think they can pull that up. From what I read that if you get a PCM that had sentry key it can't be unprogrammed to not look for the sentry key module. Not sure about that though.

You will be able to use the PCM without VIN programming, but properly it should be programmed with your vehicle mileage and the VIN.
 
Last edited:
Thanks again Talyn, I am still working with ACX on this and they are still compliant trying to get me the right part. I also called a Jeep dealer and they confirmed that the P56041668A- number is the correct computer for my application. I'm convinced the unit I received from ACX is defective and assuming they programed it correctly and if they had given me a solid unit, I would have a working, inspection passing XJ right now. There is something majorly wrong with the holesaw/chisel programmed unit I have in my hands right now.
 
Well they are sending me another unit, this time it will be the first unit they sent me just programmed as a manual. Hope this one works!
 
Alright I got the 3rd computer in last night and it's correct! No CEL and it runs just beautifully. It even turns the shift light on when it wants me to shift. The P/N ended up being P56041667AF, according to my scanner. Drove it to work today and hopefully they can squeeze me in for inspection tomorrow.
 
Finally I find someone swapping the auto for the manual. I plan on doing this in the future. I figured there would be some issues with the PCM and TCM seeing as how the TCM will be missing completely. I had just planned on getting a PCM from a manual Cherokee. Mine is a '99 and it doesn't seem like a common swap, which brings me to my next issue, actually finding the parts. Where did you get it all? Donor rig? Also, is it necessary to leave the NSS in circuit? If you have the PCM from a manual tranny Jeep it should be unnessasary.. Although the reverse lights may be a problem, maybe some custom circuitry there. Anyway I'll be watching because this is my future plan..
 
XJ runner said:
Finally I find someone swapping the auto for the manual. I plan on doing this in the future. I figured there would be some issues with the PCM and TCM seeing as how the TCM will be missing completely. I had just planned on getting a PCM from a manual Cherokee. Mine is a '99 and it doesn't seem like a common swap, which brings me to my next issue, actually finding the parts. Where did you get it all? Donor rig? Also, is it necessary to leave the NSS in circuit? If you have the PCM from a manual tranny Jeep it should be unnessasary.. Although the reverse lights may be a problem, maybe some custom circuitry there. Anyway I'll be watching because this is my future plan..
Click to expand...

XJ runner,

I am working on a detailed writeup which should answer your questions in detail, but to sum it up: Yes the PCM misses the TCU, which is why you need to do the PCM swap. I had a donor rig, but it was a 94 and mine is a 00 so there were some difference there that will be highlighted in my writeup. The NSS should be removed from the circuit and this will be a big part of the writeup. You are correct it is unnecssary except for the starter solonoid circuit and the reverse lights. I will post a link to the writeup to close this thread, hopefully today or very shortly thereafter.
 
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