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Thread: 3800 engine swap question

  1. #1

    3800 engine swap question

    Hey all,
    Bought a black 98 GT with just over 103k. Ran beautifully and suddently threw a rod bearing (we think-haven't torn it completely down yet). Car is in good shape but obviously not well-maintained motorwise.

    Found a 3800 from a 03 LeSabre with 1400 (yes 1400) miles on it. Installed new motor and a couple of sensors from the GP. Now getting Service Engine Soon light. Scanner said tranny code P1810. Reset it and tranny shifted great until we got to our destination. Restarted car, engine light came back on and car would not shift out of 2nd. Shut car off, restarted and it shifted fine in all gears again, but engine light still on.

    We are using the 03 tranny and MAF, but using the 98 PCM. I'm told in other forums that we have to replace the PCM with an 03 PCM. Can it be reprogrammed using the HP Tuners software or do we really need to buy a different PCM?

  2. #2
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    Quote Originally Posted by 1gr869 View Post
    Hey all,
    Bought a black 98 GT with just over 103k. Ran beautifully and suddently threw a rod bearing (we think-haven't torn it completely down yet). Car is in good shape but obviously not well-maintained motorwise.

    Found a 3800 from a 03 LeSabre with 1400 (yes 1400) miles on it. Installed new motor and a couple of sensors from the GP. Now getting Service Engine Soon light. Scanner said tranny code P1810. Reset it and tranny shifted great until we got to our destination. Restarted car, engine light came back on and car would not shift out of 2nd. Shut car off, restarted and it shifted fine in all gears again, but engine light still on.

    We are using the 03 tranny and MAF, but using the 98 PCM. I'm told in other forums that we have to replace the PCM with an 03 PCM. Can it be reprogrammed using the HP Tuners software or do we really need to buy a different PCM?
    Have you tried using the transmission settings from an 2003 transmission? The 4T65E transmissions are not all interchangeable. Almost every year, there are a few small differences.
    Last edited by Bedwards; 01-03-2011 at 02:20 PM.

  3. #3
    You need to use an 03 pcm with 03 4t65e's as the electrical components were changed for that year

  4. #4
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    He's right. I think the pressure control solenoid and a few other valve body components were changed.

  5. #5
    That's what I'm hearing, so you guys are giving me consistent info. Where I'm getting confused now is if we should use an 03 Grand Prix PCM or an 03 LeSabre PCM. If the gear ratio is different would the 03 Grand Prix PCM not work?

    I'm just trying to avoid buying the wrong PCM.

    nice GP, oakleafresin!
    Last edited by 1gr869; 01-03-2011 at 04:43 PM.

  6. #6
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    Quote Originally Posted by 1gr869 View Post
    That's what I'm hearing, so you guys are giving me consistent info. Where I'm getting confused now is if we should use an 03 Grand Prix PCM or an 03 LeSabre PCM. If the gear ratio is different would the 03 Grand Prix PCM not work?

    I'm just trying to avoid buying the wrong PCM.

    nice GP, oakleafresin!
    I'm not sure how your car would function with a LeSabre PCM. The security settings/electronics would be different (I'd assume). I would get a Grand Prix PCM and tune it to the transmission settings you need.

  7. #7

    Update

    Bought a PCM from a 01 Grand Prix and one from a 03 LeSabre. The LeSabre PCM lit up the dash like a Christmas tree and the car stalled. Plugged in the 01 GP PCM and the car runs but now is throwing codes P0418 and P0412. If we put the 98 PCM in then all we get the tranny code P1810.

    Should we jsut swap the 03 tranny with 1400 miles on it for the 98 tranny with 110k miles on it and then use the 98 PCM?

  8. #8
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    Quote Originally Posted by 1gr869 View Post
    Bought a PCM from a 01 Grand Prix and one from a 03 LeSabre. The LeSabre PCM lit up the dash like a Christmas tree and the car stalled. Plugged in the 01 GP PCM and the car runs but now is throwing codes P0418 and P0412. If we put the 98 PCM in then all we get the tranny code P1810.

    Should we jsut swap the 03 tranny with 1400 miles on it for the 98 tranny with 110k miles on it and then use the 98 PCM?

    03 LeSabre PCM with 03 Grand Prix bin/osid? Or just the 03 LeSabre with the 03 LeSabre bin/osid?

    The hardware doesnt mean all that much (there are a few key ranges of of hardare), but the os defines most of what you need.
    97 Grand Prix GTP (not going to bother listing mods in detail) 1 messed up 97 PCM with about 30-50% of a 2003 calibration and parts of a few others.

  9. #9
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    i think you can switch over the trans inner wiring harness and be ok but im not sure, contact dave from trippleedgeperformance.com he knows everything about these transmissions.

    just to be safe id get he 03 lesabre pcm and make sure its the right engine for the pcm. to get the right vin on there you'll probably need to email you bins to tech support so they can make the vin and osid's match.

    the tranny code from the 98 pcm is probably because the gear ratio is different then what you have in there but thats just a shot in the dark.

    you should make sure the trans file matches the car the trans came from and the same goes for the engine to start off.

  10. #10
    Returned the 01 Grand Prix PCM and swapped it for an 03 Grand Prix PCM. BINGO!! No dummy lights and runs like a 1400 mile motor should. Shift points are a little different but getting better mileage with it.

    Thanks guys for your help!

  11. #11
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    Good to hear.. Sounds like you just need the 03 GP os to communicate correctly.
    97 Grand Prix GTP (not going to bother listing mods in detail) 1 messed up 97 PCM with about 30-50% of a 2003 calibration and parts of a few others.