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Thread: Convert OBDII Northstar to OBDI ???

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    tobygaff is offline Cadillac Owners Member
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    Convert OBDII Northstar to OBDI ???

    I have a 97 Northstar engine with the throttle body and sensors for the OBDII setup. I also have a custom computer and wiring harness for an OBDI Northstar. I need to convert this 97 motor back to OBD I. I know the throttle body is different, is this a direct swap or do I need an adapter to make the old throttle body work? Is there anything else that needs swapped?

    If anyone has the OBD I parts that would like to trade for the OBD II parts, let me know.

    Thanks for any info you can provide.


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    CadillacSTS42005's Avatar
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    Re: Convert OBDII Northstar to OBDI ???

    totally
    different
    engine

  4. #3
    tobygaff is offline Cadillac Owners Member
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    Re: Convert OBDII Northstar to OBDI ???

    Ok, maybe I am not asking the right thing.... I have a 97 engine, and I need to convert it to a 95 style engine. Is that OBD II to OBD I? I thought that 97 is when the OBD II stuff started, but I could be wrong.

    According to the people that made the harness, it will work if I put the old style throttle body on it. I hope they are correct. Otherwise I wasted a lot of money on this engine.

    Where do I look to identify exactly which engine that I have so that we know what we are referring to? Everybody refers to the 9 or the Y engine, but I don't see any numbers that seem to point to identification like that.
    Last edited by tobygaff; 12-31-08 at 01:17 PM.

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    Re: Convert OBDII Northstar to OBDI ???

    i fully understand you
    and my statement still stands
    sell it and buy a 93-95 n*
    the intake
    sensors
    are completely different of this i am sure
    then i am also pretty sure the heads are different as well

    y and 9 refer to the 8th digit of the car of origins vin
    y is the L89 275 HP N*
    9 is the L37 300 HP N*

  6. #5
    tobygaff is offline Cadillac Owners Member
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    Re: Convert OBDII Northstar to OBDI ???

    You are not making my day. I don't have the original cars VIN. Is it on the engine anywhere?

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    Re: Convert OBDII Northstar to OBDI ???

    i know theres a stamp on it somewhere
    and you can use that info to determine what it is
    but as far as a simple Y or 9 nope sorry

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    Re: Convert OBDII Northstar to OBDI ???

    There's a VIN derivative (part of the original vehicle VIN) stamped on a pad on the right front side of the block just below the front side of the cylinder head. Not far from where the VSS bolts to the transaxle......

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    tobygaff is offline Cadillac Owners Member
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    Re: Convert OBDII Northstar to OBDI ???

    Yep, found it. Looks like the last digit is a 9, I also see on the other side that the casting marks on the block show a 96, so it may actually be a 96 motor. Are they really that different from a 95 motor?

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    Re: Convert OBDII Northstar to OBDI ???

    95 (obd1) will work on a 96+ if you swap the intake
    a 92*(late Allante)-94 is not interchangeable with any other years...
    i guess there SOME way to make a 96 work with a 95 obd set up so long as you get the 95 year only intake
    but no way to convert it to a 92-94 set up
    again all this work
    your much better looking for a N* already set up for obd1

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    tobygaff is offline Cadillac Owners Member
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    Re: Convert OBDII Northstar to OBDI ???

    I am going to play around with it. If the throttle body is the only thing that is different, I know that I can machine an adapter plate to let the old throttle body work on the new intake. Shouldn't be too hard.

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    Re: Convert OBDII Northstar to OBDI ???

    tb isnt the difference
    its the whole intake

  13. #12
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    Re: Convert OBDII Northstar to OBDI ???

    Quote Originally Posted by tobygaff View Post
    Ok, maybe I am not asking the right thing.... I have a 97 engine, and I need to convert it to a 95 style engine. Is that OBD II to OBD I? I thought that 97 is when the OBD II stuff started, but I could be wrong.

    According to the people that made the harness, it will work if I put the old style throttle body on it. I hope they are correct. Otherwise I wasted a lot of money on this engine.

    Where do I look to identify exactly which engine that I have so that we know what we are referring to? Everybody refers to the 9 or the Y engine, but I don't see any numbers that seem to point to identification like that.
    What kind of PCM is this?

  14. #13
    tobygaff is offline Cadillac Owners Member
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    Re: Convert OBDII Northstar to OBDI ???

    It is one of the Howell Engineering standalone PCMs for the 92-95 Northstar. Unfortunately I bought a 96 Northstar because I thought I could make it work. They said that the only difference is the throttle body.

  15. #14
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    Re: Convert OBDII Northstar to OBDI ???

    Quote Originally Posted by tobygaff View Post
    It is one of the Howell Engineering standalone PCMs for the 92-95 Northstar. Unfortunately I bought a 96 Northstar because I thought I could make it work. They said that the only difference is the throttle body.
    That PCM has NO trans support. I know the HISTORY on YOUR PCM. I know who purchased it new and all the history. I thought it might surface again.

  16. #15
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    Re: Convert OBDII Northstar to OBDI ???

    The only aftermarket Trans controller I have been able to find is made by PCS powertraincontrolsolutions $750+ just in case your looking. If you found another brand please let me know, I've been shopping around.

    From the parts I've aquired over the years the 93-95 intake has only a 4 bolt setup with about 1 inch spacers to the mostly aluminum intake and the newer heads I have (casting year 1998) have a 10 bolt pattern. I tried to line up the spacers with the 4 bolt pattern and they are close, the spacers have a locating dowels on each end where a threaded holes are now on the 98 heads so you would have to mill/drill it out.

    Please note I never test fitted the 98 heads on my 94 block yet. I'm not sure of the head to head distance gap for the intake. If you have access to a milling machine you might make it might work. I've make some assumptions that you are going to track down an older intake, have a background in machining and your custom harness will connect to the intake you aquire.

    Hope this was helpful. J

    P.S. If you are thinking about going another route and selling the PCM please PM me, I have a friend looking for a unit like this.


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