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    ECU & Wire Harness Questions

    So I'm finally swapping to a DOHC motor.....

    The question that I have is: I'm going to be getting a Protege LX, that is what I'm going to be getting the motor out of. The LX is an automatic while mine is a 5-speed. Can I still use the ECU out of the Auto LX?? Are there different ECU's for the Auto's and manuals??

    Is it really difficult to get the wiring harness out?? Am I going to have to remove the dash or anything like that?? We just swapped motors on my brother's Geo Storm and we had to remove both fenders, and the front bumper.

    Well thanks guys you are always very helpful.



    #2
    no the harness is really easy to get out. But you can't use the harness from a automatic. You may be able to modify it... but you would have to research that with a FSM .. It took Adam like 10 minutes to get the harness out of his protege.

    You may be able to use the ecu temporarily..
    But I am not sure.

    why don't you look for a 5 speed LX..

    Bruce
    photo album|photo album 2 (pbase)

    dbest1a AT yahoo DOT com

    Comment


      #3
      I would get a 5-speed LX, but I'm trading for the car for some work. Hmmmm.... Do you know why the ECU won't work? Is there maybe a way to bypass the Auto Tranny settings or something?


      Comment


        #4
        I think you can use the ecu temporarily, but I know the 5 speed ecu has 3 plugs and the auto has 4..
        You may have to run the wire for the VICS manually also.
        Are you getting the LX tranny or using the DX tranny you have..
        Bruce
        photo album|photo album 2 (pbase)

        dbest1a AT yahoo DOT com

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          #5
          For right now I will be using the SE tranny that I have.........I will be upgradeing soon though seeing as I almost have everything to turbo my car except engine management.


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            #6
            SO suppose I still use the SE ECU and just wire in the VICs, The redline would still be at 6.5K wouldn't it? Aren't there going to be other major discrepencies that will hinder performance using the SOHC ECU??

            So the reason I can't use the DOHC ECU & Harness is because it is an Auto, right? Or is it just the harness? I only remember removeing two wires from dropping my tranny to replace the clutch. Do the DOHC Auto & Manual ECU's control the transmission also or is there a different transmission module for that? Thanks.


            Comment


              #7
              Originally posted by Tweeaks
              SO suppose I still use the SE ECU and just wire in the VICs, The redline would still be at 6.5K wouldn't it? Aren't there going to be other major discrepencies that will hinder performance using the SOHC ECU??

              So the reason I can't use the DOHC ECU & Harness is because it is an Auto, right? Or is it just the harness? I only remember removeing two wires from dropping my tranny to replace the clutch. Do the DOHC Auto & Manual ECU's control the transmission also or is there a different transmission module for that? Thanks.
              The vics is controlled by the ecu...

              You should be able to use the ECU temporarily, but I would advice to try and get your hands on the 5 speed ecu, when you get a chance.

              I am not sure about the tranny, but I know when I compared a 1.5L 5 speed harness and an auto harness. they were the same untill I got to the tranny plugs.
              Bruce
              photo album|photo album 2 (pbase)

              dbest1a AT yahoo DOT com

              Comment


                #8
                When you say I "should" be able to use the harness temp. you mean the LX harness correct?

                So the ECU settings are different for the manual and auto, because the auto ECU is going to be set-up for the shift-points and all of that stuff right?

                So useing the auto ECU is only going to give me minimal gains if I can use it, right?

                If the ECU will work just for daily driveing (ie. no hard driveing) then I guess I will just use it untill I can save up for full engine management...........or just park my car until I am finished with everything that I want to do to it.


                Comment


                  #9
                  A 5 speed ecu for a 1st gen LX, is not hard to find. Most junkyards will have them.. and I doubt it will cost much with some haggeling
                  Bruce
                  photo album|photo album 2 (pbase)

                  dbest1a AT yahoo DOT com

                  Comment


                    #10
                    well to help you out a little bit here, first off you don't need the wiring harness from the LX you can actually use your old SOHC, the only thing you would have to do is to tap into the wiring harness so you can plug and control you VICS, if you need more info on that just email me and i'll give you a page that explains how to do it by detail, now as for ecu, you can't use the auto ecu for it has it own setting and is not made to have the gears changed manuelly since it controls a module which does so, plus 5spd ecu's and auto are very different and also have different fuel cuts and redline, my LX would redline at 7000rpm and fuel cut was at 7200rpm, auto driven cars redline at 6500rpm and fuel cut if i'm correct is around 7000rpm or 7200 not shure, as for finding an ecu its easy look on ebay they run there for about 20 dollars, i bought my v6 ecu for 25dollars, also if anyone is interested i'm selling a 91 lx DOHC engine with ecu for $150
                    92 323 with KF-ZE V6 swap done by me, cold air intake, 2 1/4 header back piping, ported throttle body with spacer, NOW FOR SALE FOR $2500, email me at dezznuts59@aol.com

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                      #11
                      also if you do use you auto ecu you better expect that check engine light to appear, and the car might not even run, or the ecu might drop in safe mode
                      92 323 with KF-ZE V6 swap done by me, cold air intake, 2 1/4 header back piping, ported throttle body with spacer, NOW FOR SALE FOR $2500, email me at dezznuts59@aol.com

                      Comment


                        #12
                        Well I swapped in the DOHC. Used the Auto Harness, and ECU....No problems yet, been running it for 4 days and it runs strong. Thr first few days I had the check engine light on almost always, then yesterday I remembered that I didn't plug in the O2 sensor.....DUH .

                        The Check Engine light hasn't come on since.

                        So in conclusion the Auto ECU can be used with no problems.

                        Are you guys sure that the Auto pro's don't have another computer for the tranny????


                        Comment


                          #13
                          Yes, they do, a TCU, which is located near the steering column I believe.

                          To be clearer, if I'm not mistaken, the early models had the TCU integrated into the ECU, while the later ones were seperate. I can't verify this myself though. But some models (if not all) definately have a seperate computer.

                          Congrats on your DOHC swap, how the hell do you rip out a harness in 5 minutes though? Mine is all tied up inside the car. BTW, I think the Auto LX uses a 4-wire Throttle Position Sensor instead of 3-wire, but I guess you haven't encountered any problems with that.
                          Last edited by charles; 01-14-2004, 03:58 AM.
                          2006 Mazda 3 hatchback manual

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