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  1. #1
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    5.2 PCM in a 5.9

    Hi

    I just found out, while searching for pcm part numbers, that my 98 niner has a 5.2 pcm in it.

    p/n is 56041 515AC

    Now what are my best options ? Can I go to dealer to get Mopar ECU tune flashed in it ? Do I need to change ECU if I want to go with SCT or SuperChips ?

    I hope I have a real 5.9 in this thing .... Any way to confirm this ?

    thank you
    Alex

  2. #2
    Forum CONDUCTOR Man Z88Z's Avatar
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    Alex, it depends on how far you're going to take this.

    First, most important thing is - if at any point you're thinking of getting an SCT tune you don't need to change that PCM!

    Confirm this with Ryan/flyinryan of course, but from everything I've learned about SCT tuning it overwrites all the existing tables - so it doesn't matter if it started out as a 5.9PCM or a 5.2 PCM...

    For that same reason, you don't want the MP PCM if you're going with SCT. You'd be overwriting a (semi)valuable piece and there's no advantage to that.

    If you do decide to get a different PCM, just make sure you get the right one - FED vs CALI emissions. You can put a FED spec PCM in any ZJ, and it will ignore the LDP/Leak Detection Pump that the CALI ZJ has. You can not put a CALI spec PCM into a FED spec ZJ as you'll get a CEL/MIL from the CALI PCM not seeing the LDP it's looking for. (I think you can just plug in the LDP and a bit of plumbing as the LDP wiring is there on all ZJs, but why bother?)
    Probably easier to get the FED PCM unless you still need the CALI one to pass emissions where you live...




    As far as the motor, if you look way up on the block under the driver's side exhaust manifold the size is cast onto the block. I honestly can't remember if it says it in liters or in cubes, but I think it's in cubes.
    It's way up on the block and kind of a PITA to see. You'll need to get way under there and check it with a good light.

    There's also a serial number on the front of the block just under the driver's side head - but I don't know if you can even see that with the power steering pump being right there and all... Nor do I recall what serial number is 5.9 vs 5.2 or whether it actually says engine size there.

    For all that - I believe there's a much easier way to confirm it: I've seen and/or pulled five 5.9 motors and three 5.2 motors. In all of those cases, the 5.2 vs 5.9 driver's side motor mounting "ears" (on the block, where the ZJ brackets attach...) were different.
    The 5.9s only have 3 bolt holes on the ears that stick out. In fact I think there's only 3 ears. On the 5.2s they all have four bolt holes on the driver's side ears. (ya, seems kind of backwards where the 5.9 puts out more torque/hp but has less attaching points, lol)


    Couldn't hurt to check the tranny too. The 5.2s 44RE has a pretty much rectangular pan. The 5.9's 46RE has a bit of a kick-out at the right front where the dipstick tube is.



    On that note, since you seem to have doubts - did you ever confirm it's a real 5.9 Jeep?

    It should have my s/n in the VIN - although even the dash with it's VIN can be swapped!
    The only 100% certain place to find it is under the rear passenger side seat. Lift the seat and pull up the rug from the top of the "rail" or frame work that the seat hinge bolts too. You'll find the VIN 'spot engraved' right on the top of the rail there. It's actually fairly hard to see as the hinges hold the rug pretty tight to the top of the rail - you really have to push the rug back and get right in there to see it.

  3. #3
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    Alright, I followed your steps. I was pretty sure I have a real 5.9 ZJ and it is. I also found out I have a Magnum 360 engine. Only thing is my PCM, which is a 5.2

    I also found out I have some really long bump stock, 2 coil isolators stacked in front (is this oem ?) and a 6' long front diff vent tube. I think that Jeep once used to be a trail rig. Maybe it went in deep water and broke oem PCM.

    Now I'm looking at either a oem 5.9 PCM (already got an offer), a MP 5.9 PCM or a good price on a SCT handheld. My no1 priority would be to find a MP PCM.

    Thank you very much again for all your help. If you ever want to sell your Mopar Performance PCM, I would buy it if it is possible to trick it into a fed pcm.

  4. #4
    RallyJeep GO
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    The diff vent tube up to the airbox is stock. Should only have 1 coil isolator per spring though. As far as bump stops, at stock ride height (18" hub to fender), there should be about 2.5" of travel before hitting the front bumpstops. Adjust this based on actual ride height to determine if the bumpstops are stock length or not.
    1998 ZJ 5.9 Limited - Deep Slate
    Mods: Big trans cooler, 231 swap, Indy MA-X heads prepped by IMM, Comp 20-744-9 cam, 1.7 HS roller rockers, 52mm TB, Airgap manifold, DT headers and full 3" exhaust, SCT tune homebrewed by me, Martin Saine valve body, B&M tranny pan, magic suspension made from unicorn tears, power steering cooler, lots of lighting mods

  5. #5
    Member csouers's Avatar
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    Is Z88Z in the vin? If not, it's not a legit 5.9.

    Edit. Look underneath the rear passenger seat. The body vin will be stamped into the metal somewhere near there. I believe it's on top of lip just under the seat.

  6. #6
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    Quote Originally Posted by comptiger5000 View Post
    The diff vent tube up to the airbox is stock. Should only have 1 coil isolator per spring though. As far as bump stops, at stock ride height (18" hub to fender), there should be about 2.5" of travel before hitting the front bumpstops. Adjust this based on actual ride height to determine if the bumpstops are stock length or not.
    Then it might be all oem. I installed a Spectre air hat with 4'' short ram tube and ditched the oem air box, maybe that's why I didn't notice the long diff vent tube.

    I checked and it seams to be about 2.5'' of travel so the bumpstops might actually be oem.

    Either this Jeep was reverted to 100% oem state or it never was a trail rig. I don't really care at this point. Thank you for clarifying this.



    Quote Originally Posted by csouers View Post
    Is Z88Z in the vin? If not, it's not a legit 5.9.

    Edit. Look underneath the rear passenger seat. The body vin will be stamped into the metal somewhere near there. I believe it's on top of lip just under the seat.
    Yes it was, I checked yesterday and everything is fine. I was also able to see the first 4 digits stamped on driver's side engine block. The fourth one is a 2, so definitely a magum 360.


    thank you all for that information and tips on how to verify everything.

  7. #7
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    If I buy a SCT Handheld, can I use a tune from someone else SCT ?

    I mean, let's say I have someone who accept to give me a copy of his tune, can I use it in my Jeep or each tune has to be made for a specific Jeep ?

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    Forum CONDUCTOR Man Z88Z's Avatar
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    I'm gonna say no for a couple of reasons.

    Pretty sure the SCT will only work for one PCM at a time. I believe it interacts with the PCM and reads it's serial number.

    For you to even use his tuner, he'd have to remove the tune from his Jeep/PCM (return it back to the stock tune) for it to be able to be used on another PCM/vehicle, plus it will only load the tune 3 times. I'm pretty sure that '3 times' rule applies even if it's being used on the same PCM but I can't say that with 100% certainty.

    If you mean can you download a tune, like one he got emailed to him and has on his home computer or whatever, and download that onto a different handheld unit as in two different handheld units - I'm going to say that (probably, like, I'm pretty sure) won't work either.
    Totally guessing at this part but I imagine the emailed software itself sees the serial number of the tuner itself, or is written to only interact with the s/n from one tuner


    SCT and the tuners themselves need to do something to protect their business. Otherwise there'd just be a few tunes out there and people would be swapping them around like mad. One tune would be in dozens of vehicles and they'd lose a ton of business.
    I believe they do this by limiting what the tune and/or it's handheld device can interact with.
    Last edited by Z88Z; 05-01-2015 at 08:01 AM.

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    That is a nice explanation ! You said that SCT handheld toes with the PCM but what happens if I buy the PCM with the handheld ?

    Also do you think I can see any performance difference between my 5.2 pcm and Mopar PCM / SCT on a stock ZJ ? Only thing I have is Spectre short ram and soon 3" exhaust + custom downpipes. I found a Mopar unit in Florida but I wonder if it's worth it. I can buy it for 160$ usd or close to 200$ cad. What do you think is my best option : stay 5.2, go Mopar, trying to find sct + pcm or go 5.9 stock pcm ?

  10. #10
    Forum CONDUCTOR Man Z88Z's Avatar
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    If you buy an SCT tuned PCM and it's handheld SCT tuner, it will have the tune in it - provided that's how it was when it was removed. And that's assuming it was tuned for something close to stock like yours - a tune for a "built" motor probably won't be good for yours.

    Still though, after 3 loads the tuner will be locked so if the PO loaded it 3 times for whatever reason and went back to the stock tune it would be useless. You'd still have to pay to have it unlocked and pay Ryan for the tune.

    MP PCM should feel a bit better than your 5.2 PCM, but from what I've heard the MP PCM isn't really a huge difference over the stock 5.9 PCM.


    IMHO, just save your money and go SCT.

    Maybe get a stock 5.9 PCM for the time being - but only if you can find one fairly cheap! ($50 or something?) Just remember any money you put towards any of this stuff is money that's being thrown away if you eventually go SCT.

    Granted you'll make out a bit if you get a "cheap" SCT along with the tuned PCM - but that combo only shows up on rare occasions. That's assuming the seller is honest about what he has and whether it's locked and the tune is what you need.

    Ryan can tune your 5.2 PCM to run the 5.9 better than the MP PCM. Any money towards the other stuff is really kind of a waste.

  11. #11
    RallyJeep GO
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    The tuner doesn't lock after 3 loads, but after using with 3 different PCMs.
    1998 ZJ 5.9 Limited - Deep Slate
    Mods: Big trans cooler, 231 swap, Indy MA-X heads prepped by IMM, Comp 20-744-9 cam, 1.7 HS roller rockers, 52mm TB, Airgap manifold, DT headers and full 3" exhaust, SCT tune homebrewed by me, Martin Saine valve body, B&M tranny pan, magic suspension made from unicorn tears, power steering cooler, lots of lighting mods

  12. #12
    Forum CONDUCTOR Man Z88Z's Avatar
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    Quote Originally Posted by comptiger5000 View Post
    The tuner doesn't lock after 3 loads, but after using with 3 different PCMs.
    Ahh, good. I stand corrected.

    So, you could UL and DL multiple times (more than 3...) to one PCM and it wouldn't matter, wouldn't lock it, etc? An unlikely scenario I guess just asking so I don't misquote again, lol.

    Am I right in thinking it will only work with a second PCM once the first PCM has been restored to the stock tune? Like, you can't use the 3 tunes it holds to tune 3 different PCMs concurrently, right?

  13. #13
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    Quote Originally Posted by Z88Z View Post
    Ahh, good. I stand corrected.

    So, you could UL and DL multiple times (more than 3...) to one PCM and it wouldn't matter, wouldn't lock it, etc? An unlikely scenario I guess just asking so I don't misquote again, lol.

    Am I right in thinking it will only work with a second PCM once the first PCM has been restored to the stock tune? Like, you can't use the 3 tunes it holds to tune 3 different PCMs concurrently, right?
    You've got it. Only 1 PCM can be tuned at a time, and you can only tune 3 different ones ever without SCT's intervention. But once you tune a PCM, you can re-tune that one as many times as you want (I've flashed mine well over 100 times).
    1998 ZJ 5.9 Limited - Deep Slate
    Mods: Big trans cooler, 231 swap, Indy MA-X heads prepped by IMM, Comp 20-744-9 cam, 1.7 HS roller rockers, 52mm TB, Airgap manifold, DT headers and full 3" exhaust, SCT tune homebrewed by me, Martin Saine valve body, B&M tranny pan, magic suspension made from unicorn tears, power steering cooler, lots of lighting mods

  14. #14
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    to make sure, anyone can confirm if you can use a tune coming from another pcm ? or each tune is pcm locked or vin locked ?

  15. #15
    Forum CONDUCTOR Man Z88Z's Avatar
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    I'd go by what Rob/comptiger said.

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    A small update on this :

    I bought a 9550 sct handheld from a member on this forum with 2 remaining slots. To my surprise, his tunes were still in it. So I tried to flash my pcm and it worked ! I saw 87, 91 and 93 octane tunes. Since I run on 91 (I live in Québec, Canada and we only have 91 or crappy 94 octane in here) I flashed the 91 octane tune and immediatly saw a huge upgrade.

    When I plugged the handheld in my truck, it asked me if I wanted to use another slot for a new pcm. I selected yes and I was then able to flash whichever tune the handheld got. I'm really happy about this !

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