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Thread: '94 Jeep Cherokee Tuning

  1. #81
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    Re: '94 Jeep Cherokee Tuning

    Quote Originally Posted by sev80 View Post
    Gents, (wowzer and A_Kelly), where did you source the 781 cal? Im wondering if it is really from a gulf states emissions ecu or if MPtune is compiling and putting something in there to say that. I want to pop the cal back in my truck and drive it around more, it felt more peppy but I didnt push it last time I tried.

    I wonder how much there is a difference between california emissions, Federal Emissions, 50 state emissions and Gulf states emissions (I have all the PCMs for each of these.)

    The original SBEC II in my 94 ZJ is cal emissions, the 381 cal is Federal emissions, the 95+ cal is 50 state emissions and the 781 cal is "gulf states" emissions.
    Please post the part numbers for your Ecus.

  2. #82
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    Re: '94 Jeep Cherokee Tuning

    Quote Originally Posted by vprtech View Post
    Please post the part numbers for your Ecus.


    My original 94 ECU with california emissions is: 56029301. It is a newer style SBEC II that has the flash chip date code on it is 6/1994

    The late 93 ECU I socketed is Federal Emissions: 56028310. It is an older SBEC II that is non flashable. The date code on it is 10/7/1993

    The near end of production SBEC II I bought as a spare is 50 State emissions: 56026948. Date code on it is 4/1995

    There's 3 ECUs above all fit a 93-95 Grand Cherokee with A/T

    The 781 ECU that ID's as "Gulf States Emissions" is the 781 one that Wowzer and A_Kelly are IDing. I'm not sure if this is a by product of MpTune compiling it or if it is actually from the gulf states.

  3. #83
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    Re: '94 Jeep Cherokee Tuning

    Quote Originally Posted by sev80 View Post
    Gents, (wowzer and A_Kelly), where did you source the 781 cal? ...
    http://www.turbo-mopar.com/forums/sh...=1#post1005818
    89 Voyager LE, 2.5T2 - rest in peace
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  4. #84
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    Re: '94 Jeep Cherokee Tuning

    Quote Originally Posted by sev80 View Post
    My original 94 ECU with california emissions is: 56029301. It is a newer style SBEC II that has the flash chip date code on it is 6/1994

    The late 93 ECU I socketed is Federal Emissions: 56028310. It is an older SBEC II that is non flashable. The date code on it is 10/7/1993

    The near end of production SBEC II I bought as a spare is 50 State emissions: 56026948. Date code on it is 4/1995

    There's 3 ECUs above all fit a 93-95 Grand Cherokee with A/T

    The 781 ECU that ID's as "Gulf States Emissions" is the 781 one that Wowzer and A_Kelly are IDing. I'm not sure if this is a by product of MpTune compiling it or if it is actually from the gulf states.
    It is a Gulf calibration, leaded fuel, so it should run in open loop.

  5. #85
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    Re: '94 Jeep Cherokee Tuning

    I cant contribute much here but i think the 4.0 rev limiter IS actually close to 6000 rpm. I remember this because we swapped from a 3.07 to 3.50 rear end in my friend's 5spd cherokee and then accidentally spun up to the limiter in 2nd when it broke loose through a puddle. Tach went to 6k.. and the water pump immediately ---- out the shaft seal, which ruined our plans to go to the track the next day and beat the 16.0 it had run stock with 3.07s.

    Dont push the red button.You hear me?

  6. #86
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    Re: '94 Jeep Cherokee Tuning

    Any updates from A_kelly or wowzer?

  7. #87
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    Re: '94 Jeep Cherokee Tuning

    Quote Originally Posted by sev80 View Post
    Any updates from A_kelly or wowzer?
    what info are you waiting for ?
    89 Voyager LE, 2.5T2 - rest in peace
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  8. #88
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    Re: '94 Jeep Cherokee Tuning

    im not waiting for anything, really. A_Kelly mentioned he was going to create a bench teser and try out the cal he built, wanted to see ifhe had any updates..

    Are you still working on IDing tables? Did you still want to use MPscan to try to find more tables?
    Last edited by sev80; 08-13-2017 at 06:46 PM.

  9. #89
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    Re: '94 Jeep Cherokee Tuning

    Looking at the FED vs Leaded calibrations, I was searching for a flag or temperature threshold to disable closed loop, however I did not find any. It appears all they did the the Leaded/Gulf calibrations was to disable the codes for O2 voltage stuck at center (0x8A28 bit 1) and O2 voltage stuck high (0x8A28 bit 2)? Also did some bench testing, and neither cals would go into closed loop unless you toggle the O2 voltage below .5 volts .

    Rev limit on all of the SBEC2 4.0L Jeep cals I've seen is 5312 (@ 0x8681 , JTEC it's 5300 rpm.)

  10. #90
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    Re: '94 Jeep Cherokee Tuning

    vprtech, is 8a28 the correct table?

    i had already noted the rpm and mph limiters in my last update.
    89 Voyager LE, 2.5T2 - rest in peace
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  11. #91
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    Re: '94 Jeep Cherokee Tuning

    As far as I know, yes.

  12. #92
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    Re: '94 Jeep Cherokee Tuning

    Quote Originally Posted by wowzer View Post
    instead of posting up new files i'm just going to use this link below and keep the most current zip file there. i probably won't be doing much work on it for a while at this point (but who knows). there's LOTS to be figured out yet

    https://dl.dropboxusercontent.com/u/.../jeep1_781.zip

    edit: Nvm! Nothing to see here! I answered my own question

  13. #93
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    Re: '94 Jeep Cherokee Tuning

    Damn it.. It looks like my socketed SBEC-II Died. Was heading out to lunch yesterday and the truck started misfiring BAD and stalling. Every time I'd start it it would run very rough and stall. DRB says "internal PCM failure"... Popped in the original sbec-2 I have and the truck runs fine..

    Not sure what to do. I took it out and it visually looks fine. I didnt put the potting material back on after socketing, so it was exposed to the elements, but I dont see any corrosion on it or anything. I just dont trust it now. Even if it runs right, I wouldnt want it to do what it did in traffic..

    Not sure what to do here. Do I try troubleshooting it? Do I get another one and socket it? hmmm...

  14. #94
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    Re: '94 Jeep Cherokee Tuning

    So the original SBEC II I socketed is definitely dead. I tried driving the truck around a bunch since July, for a while it was fine, but intermittently it starts misfiring very badly and stalling. I've kept my original, unmodified (56029301) sbec II and a wrench in the car just in case it left me stranded. That happened last week, luckily I limped it to the curb and swapped in the good SBEC II and I was on my way.

    I have a total of 3 SBEC's Currently. The one with 56028310 (federal emissions) is dead. At least I dont trust driving anywhere with it at this point... It came with a 27c256 rom, which obviously isnt flashable it's from a very early 93 Grand cherokee. The board layout on guy is slightly different than my other two SBEC-IIs are newer and flashable, however I dont have the tools to flash them.

    This weekend I decided to attempt to socket the 56026948 ecu, this one is 50 state emissions. I was successful in desoldering flash chip (getting better at doin, it is a ST28F256. The idea is for me to flash the modified 310 cal I bought from vprtech onto this ECU so I can continue to use it. I am hoping the hardware differences are minor between the 56028310 and 56026948 such that I can just socket the newer ECU, flash the chip and put it in. The problem is my stupid minipro chinese programmer will read thousands of roms EXCEPT For the #@$@#$@# 28F256! I tried setting the thing to read a AM28F256 (which is supported and has a identical pinout) and it doesnt work.

    I looked up the pinouts between the 27SF256 and the 28F256 and theyre nearly the same, the 28 series chip has 4 extra pins, of which 1 is VPP, one is NC, one is VCC and one is write enable, none of which seem critical for rom operation. Wondering if the 27SF256 will work in the newer SBECII.. Or if I need to find a new eeprom programer that will read the 28f256. I do want to read it for sure.....

  15. #95
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    Re: '94 Jeep Cherokee Tuning

    I got my reader to read the cal as a AM28f256. So I have the cal for the 56026948 ecu. It is a very late 95 and 50 state emissions like mentioned earlier.

    The problem I have now is the ECU I just socketed is dead. Arrrrgggghhh. despite successful socketing, meaning I didnt lift any pads, damage any traces, scrape off any components the damn thing fails to boot with the original rom in it. It's making a high pitched screeching noise when I give it power. The only thing I could of thought might have killed it is ESD. i used a nylon brush to get the potting material down. I was under the impression this was safe to do? I really wish I could just flash one of these things and be done.

  16. #96
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    Re: '94 Jeep Cherokee Tuning

    So upon much closer inspection of the board, I found why it stopped working after the work I did yesterday, the soldering iron tip damaged 3 traces on the back side of the board. I discovered through some continuity testing and very very close examination with a magnifying glass. Luckily there were some nearby via's i could solder to so that I could reroute those traces. I did so and viola! the board works! I dont think i'd trust this board for other than bench testing purposes at this point though. I'm sick of getting stranded due to my soldering work.

    I also did confirm that the older 28 pin boards (which have a different board layout) for which my tune was written for will work with the newer 32 pin boards. Not only is the board layout different between the two, the newer board is physically smaller than the older board...anyway, I flashed over my tune and it started right up! Woot!

    Side note: it appears these boards are built with blank roms soldered into them. The back of the board has every needed pin routed to pads that are used to flash the rom in the board. Pretty cool! I used these pads to check continuity to find my problem.

    If anyone wants the 50 state cal (56026948) from this board, I have it available.
    Last edited by sev80; 11-27-2017 at 07:35 PM.

  17. #97
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    Re: '94 Jeep Cherokee Tuning

    Quote Originally Posted by sev80 View Post
    So upon much closer inspection of the board, I found why it stopped working after the work I did yesterday, the soldering iron tip damaged 3 traces on the back side of the board. I discovered through some continuity testing and very very close examination with a magnifying glass. Luckily there were some nearby via's i could solder to so that I could reroute those traces. I did so and viola! the board works! I dont think i'd trust this board for other than bench testing purposes at this point though. I'm sick of getting stranded due to my soldering work.

    I also did confirm that the older 28 pin boards (which have a different board layout) for which my tune was written for will work with the newer 32 pin boards. I flashed over my tune and it started right up! Woot!

    Side note: it appears these boards are built with blank roms soldered into them. The back of the board has every needed pin routed to pads that are used to flash the rom in the board. Pretty cool! I used these pads to check continuity to find my problem.

    If anyone wants the 50 state cal (56026948) from this board, I have it available.
    i'll take if. i'll disassemble it and set it up for mptune to see how it compares to the 781.
    89 Voyager LE, 2.5T2 - rest in peace
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  18. #98
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    Re: '94 Jeep Cherokee Tuning

    Wowzer's back!!!! Hopefully these cals help getting everything mapped out.

    Here's a 948 cal (50 state emissions)

    https://www.dropbox.com/s/g4jnhit9ue...26948.BIN?dl=0

    here's the older 310 cal (fed emissions)

    https://www.dropbox.com/s/f0m5ja79bz...0jeep.BIN?dl=0


    Will MPTune read/flash the Jeep SBEC II if it's bootstrapped? I hacked off a 60-way connector from a dead jeep and got my SBEC booted and communicating via SCI on the bench.

  19. #99
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    Re: '94 Jeep Cherokee Tuning

    you need to ask rob lloyd. i think flashing requires an adapter to apply a 20v programming charge. don't know about reading. rob is using a scaled down version of mptune to do the reading/flashing of the neon fcc chips i believe, at least as far as those routines are required.
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  20. #100
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    Re: '94 Jeep Cherokee Tuning

    Quote Originally Posted by wowzer View Post
    you need to ask rob lloyd. i think flashing requires an adapter to apply a 20v programming charge. don't know about reading. rob is using a scaled down version of mptune to do the reading/flashing of the neon fcc chips i believe, at least as far as those routines are required.
    Hmmm that's exactly what I was unsure about was whether the late sbec-IIs require 20v for programming. The ST28f256 in them, it only requires 12v for programming according to the datasheet, hence my curiosity.

    Sorry for all my n00bish questions, I really find this stuff fascinating.

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