OBD2 in a OBD1, HELP

[Ryan Stout]

Alright guys, I just did a A4 to M6 swap and found a 1995 ECU and full wiring harness locally for $150, snatched it up figuring I could use it, cut off all the EVAP and EGR connectors, a few that are unused, and basically simplify my wiring in my car. Well first off I've been driving it with the A4 ecu for a month or so now, works fine, I plug in the '95 ECU I bought and it runs the same, so I know the ECU will work. BUT, I was outside doing the wiring like I said before, well the coil only has one connector where as mine on the car has 2 that plug into the 1 coil. Now, can I cut it off and wire my old connector(s) in and use it? I did some looking and this might actually be a '96 harness (due to the coil connector problem), but the ECU still works even with no crank sensor on my old harness. Could someone please set me straight? Thanks!

[Black96z28]

1995 pcm was obd1, with an obd2 style DLC. i believe from 93-97 the pcms can be swapped without changing wiring harnesses. you best option would have just been to run your stock harness with the new computer. obd 2 is the only setup that uses the crank sensor, also with a '95 computer being obd1 it wouldnt need it. maybe just use your old harness?

Side note, is your car a 93? if it is, it did not have a mass air flow meter, and MAF used a 3 pin connector close to the coil.

[Ryan Stout]

Its a 95, so will the new ECU work alright? I haven't driven it yet.

[Ryan Stout]

Also, I'm using Tunercats, where do I adjust the temp that my fans kick on? I can't seem to find it anywere.

[Black96z28]

i dont see why your new pcm wouldnt work, in tunercats the fans kick on in ecm comstants.

[Ryan Stout]

I was just guessing that since its got a CPS it wouldn't like the '95 that doesn't have one. Call me stupid, but I still don't see where you adjust when your fans kick on. Also would you tell me what I do to tell it its a 6spd now instead of an auto? It seems like all I do is uncheck the box in the ECM switches but that seems way too easy. Thanks for all your help, you've been awesome .

[Black96z28]

it is simply that easy, it just tells the pcm whether to pay attention to the definitions for the operations for auto. on mine, its fan kick on vs. oil temp, right above the fuel cutoff for speed and rev limiters, quite a ways down the list. now, i suppose i could have been playing with the wrong variables myself, but i beleive that is the only way to adjust when the fans kick on.

As for the CPS, if your harness has the plug for it and you dont have it on your engine, as long as you are using the 95 obd1 pcm, it wont matter, because it isnt used on that computer. if your car has one, and you have a 95 computer plugged in, it still wont matter, because the obd1 pcm doesnt use that input for anything. So, the only problem would be if you put a 1996+, obd2 computer in your car and didnt have the CPS.

[Ryan Stout]

You're the man, if you were close to me I'd buy you a beer. Thanks! I'll probably have a lot more tunercats questions later when I get my injectors.

EDIT: Can I reflash the 96+ ECU to a '95? Last night I took out my 95 wiring and redid it after looking at my new harness. If I can't redo it do you want to buy it?

[Black96z28]

I have never come across this topic, but i believe that you can take a 96+ pcm and put your 95 tune on it... the software is what would decide what signals to look at. but again, ive never had experience with that.

I suppose its worth a try... haha, well my car is an obd1 converted car, i have a 1995 trans am pcm in it. From my experience it is harder/time consuming to swap pcms than just reflash it. as long as you keep your all your different versions of tune file handy.

[Twisted Z]

We first did this back in 00 to fix the deaded no shift issue.


Hit me up



BTW I am still using a 97 PCM