1996 BP wiring help, please!

Shades · Post by **Shades** » June 26th, 2007, 2:29 am

So I'm ready to drop the BP I rebuilt into my 1996 MX-3 RS... my wiring harness and ecu is from a 92 Ford Escort GT. Now there are a couple plugs that are different on the ECU end of things...

First off there are three yellow plugs that plug into the B6 ecu, and only two yellow plugs on the EGT BP ecu... what's the 3rd plug for?

Also there are some plugs that don't connect to the ecu that look the same but the pins are in different positions, do I change them around and to what?

How can I tell if it's OBDI or II?... I believe it's I, maybe?

Which harness do I use and how do I make it work?

Thanks!

atlantamx3 · Post by **atlantamx3** » June 26th, 2007, 8:47 am

Jon,

Completely disregard the B6 wiring harness and use the BP one.

Shades · Post by **Shades** » June 26th, 2007, 10:50 am

Ok, now is the Ford BP wiring harness different to the Mazda BP wiring harness?

So, besides the two plugs that hook up to the ecu what are the other ones for? I compared the other plugs and i think only one other one has the pins in the plug in different positions... I'll have to take some pictures.

Thanks Perry.

atlantamx3 · Post by **atlantamx3** » June 26th, 2007, 12:46 pm

The only thing I can think would be different is the fuel rail & associated Injector Harness.

I would get those from a Protege LX.

Just a suggestion.

shameem · Post by **shameem** » June 26th, 2007, 9:46 pm

96 model year - if not obd2 - will still have the dohc dash harness which may not plug and play with the BP ecu - you might have to cut/splice wires under the dash to make it fit.
One way to do it will be to cut the b6 dash plugs - figure out the wire color/function and splice it to the corresponding wire in the BP harness.

PoisonDrop · Post by **PoisonDrop** » June 26th, 2007, 11:41 pm

I used the same setup for my swap. The motor and ECU came out of a '92 EGT. All I remember thinking is that the Ford harness was WAY to f---ed up to use. I would have had to splice too much under the dash, and upon comparing wiring diagrams, some of the wires didn't even match up. I ended up using the complete harness from the MX-3. That way all the stuff under the dash plugs in. All the plugs on the motor should be the same.

I don't remember what the extra plug in the B6 ECU is for, but I don't think I ended up with any extra plugs that weren't plugged in after I swapped ECU's. I documented my swap in pretty good detail. If you need more info, check it out in my signiture...

PoisonDrop · Post by **PoisonDrop** » June 26th, 2007, 11:47 pm

You know, Shades, I just noticed that you posted in my swap thread. Is this the same motor you said you were going to rebuild?

Shades · Post by **Shades** » June 27th, 2007, 1:04 am

Yup that is the same motor from two years ago... haha! It ain't no stock BP that's for sure.

I think if I can't figure out the wire harness, I might have to hit the junkyard and see if the SOHC harness is closer to what I need.

Yeah on the ECU there is a 3rd plug... I'll take some pictures tomorrow when I go work on it.

I am just reading through your thread, and I have that same thing about the plugs behind the ECU...

PoisonDrop · Post by **PoisonDrop** » June 27th, 2007, 12:03 pm

Sorry, I didn't realize you had the DOHC to begin with.

The SOHC harness is EXACTLY what you need. I used the SOHC MTX harness for the MX-3, and as far as I can remember, everything plugged right in. I don't even think I had to change the pinout of that one plug under the dash, can't really remember for sure, though.

About that 3rd plug...

I'm looking at the wiring diagram for the MX-3 now. As far as I can see, the B6 ATX ECU has the 3rd plug. The MTX ECU doesn't. It doesn't look like the 3rd plug is ENTIRELY for the ATX, the pinouts on all 3 plugs are a little different. But with the BP ECU and the MTX MX-3 harness, the 3rd plug shouldn't be a factor.

PoisonDrop · Post by **PoisonDrop** » June 27th, 2007, 12:21 pm

By the way...I meant to compliment you on your motor. Very shiney! I only wish mine looked like that...

Tunes67 · Post by **Tunes67** » June 27th, 2007, 12:38 pm

I'd like to offer a different possibility.. I have no idea if it would work well... but.. since you are heading out to the junkyards anyway.. why not look for a OBDII BP Miata or Protege and get the ECU from that? Wouldnt that then allow you to use your current wiring harness then and sensors? Just a thought.

Tunes67

shameem · Post by **shameem** » June 27th, 2007, 7:09 pm

Tunes67 wrote:I'd like to offer a different possibility.. I have no idea if it would work well... but.. since you are heading out to the junkyards anyway.. why not look for a OBDII BP Miata or Protege and get the ECU from that? Wouldnt that then allow you to use your current wiring harness then and sensors? Just a thought.

Tunes67

That probably wouldnt work at all -

http://www.mx-3.com/phpbb2/viewtopic.php?t=54032

Tunes67 · Post by **Tunes67** » June 27th, 2007, 8:23 pm

That probably wouldnt work at all -

See what your missing is that AriesDudes car is a 94.. which is NOT OBDII. Shades car is a 96 and could be OBDII. So what I am suggesting is that he grab a OBDII BP ECU.. it should plug and play with his current wiring harness.. unless mazda did some really weird stuff between car models.

Now if he wants to change over his wiring harnesses. (Which he will HAVE to do if his car IS OBDII and he wants to run a OBDI ECU) then the SOHC wiring harnesses both engine bay and under the Dash would be the right choices I think.

Tunes67

Shades · Post by **Shades** » June 27th, 2007, 8:41 pm

Thanks for all the replies guys!!!

I might have to hit the junkyard for the third weekend...

I'll check that stuff out...

Also, from another forum they think it might be that hybrid OBDI and OBDII thing... which they think that third plug is for.

I'm having a hard time reading the wiring diagrams... can anyone verify that the electronic speedo wires are on the wiring harness? I'll have to check.

PoisonDrop · Post by **PoisonDrop** » June 28th, 2007, 1:36 am

Also, from another forum they think it might be that hybrid OBDI and OBDII thing... which they think that third plug is for.

My car used to have the 3rd plug. It was an automatic and, as far as I know, was only OBDI. The wiring diagram just shows some extra connections for the ATX on the 3rd plug, which is the smallest of the three.

I'm having a hard time reading the wiring diagrams... can anyone verify that the electronic speedo wires are on the wiring harness? I'll have to check.

It may be different for the DOHC, or for the 96 at that matter, but for the '93 1.6 SOHC it is the black wire with a white stripe. For the ATX ECU, it's located on the middle sized plug. For the MTX ECU, it's located on the largest sized plug. If you want I could look at your wiring diagram for you...