Thread: Calling all ECU experts, '99 harness to a '95-'97 ECU

I'm researching how to go about using a 95-96MT ECU in my 99 SEL (original harness). I'm looking at JWT's little writeup on how to do it. It states some wires need to be repinned on the harness to work with the 95-97 ECU. Okay fine. It mentions a 98 ECU. First question...Is the 98 ECU the same as my 99 ECU in terms of the pinouts and what they're connected to? Is a model # needed first to answer that question?

Assuming they are the same, the writeup states that the 112 pin need to be moved to 111 location, among other things. Is this correct? From what I've read so far, I don't think 112 is being used as a ground in my car. If anything I would think pin 106 would go to 111, since it's currently being used as the o2 ground. I'm confused.

98 and 99 are the same. Rear o2 sensor gets rewired. Can't check jwt now since I'm at work. But that's what I know off hand. Done it on an se-l and it was pretty straight foward.

You are moving the pins to be able to connect an earlier 3 wire O2 sensor into t.he car. As of now its 4

Okay. I just wanted to confirm what JWT has written up is correct for my ECU. I really don't feel like frying it.

So is the 98-99 ECU considered a 32bit? or is it still a 16bit with just a different o2 sensor setup. It isn't really clear in some of the threads I've been reading. @Vadim has a pin conversion spreadsheet for OBD1 to 16bit to 32bit. After looking at that and reading section EC of the FSM, I'm a little confused about what I have and what to do. Sorry for all of the questions, I still a noob when it comes to ECU stuff.

I'm gonna give you a few links that are in a little more detail than the jwt site.

The conversion to obd1 is simple just need an adapter harness, which I believe JKTuning sells that you can bolt in after the switch of the pins. No changes needed on the engine or anything sensor wise either.

This should help you get started to move pins.

Hank,

98-99 ECU is 16-bit.

98-99 are the same and are both 16bit. You rewire/repin exactly as the JWT .pdf says. Ive spoken to Ben@jwt and Vadim about this countless of times to be sure.

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Yup easy peasy worked well on my 99 SE-L. Just follow JWT instructions.