I purchased a used Pettit unlimited ECU from a forum member here, and UPS just got it here this morning. I disconnected the battery, and installed the ECU. On 1st crank, the car started , but immediately died. From there it would just crank, not even attempting to start. So I swapped my stock ECU back it, and she fires right up. Thinking I may have done something incorrectly the 1st time, I again installed the Pettit. Same situation, on 1st attempt it fires but immediately dies, then just cranks from there. I think install my stock ECU, and everything is fine. Any ideas as to what the problem may be? One issue I am thinking is that the ECUs are different model numbers. My car is a '94 and this ECU is from a '93, both non-cali ( I think the numbers were N3A1 and N3C1, but Ill double-check). Any help is greatly appreciated, right now I feel I may as well have threw over $400 out the window.

 

As ar as I know, the only problem is changing ECUs between non-CA cars and CA cars. The only difference is the EGR valve monotor switch. This might cause an error but otherwise the rest should be the same and work OK.

The early 93 ecu had a idle issue with the A/C and Mazda replaced them with a correct version. The non CA 94 should be good even if a different number.

Any ECU experts here?

Anyway you should have bought a PFC or something else instead of outdated technology.

 

Thanks for the input. As far as "shouldve bought a PFC", it was a big consideration, but Im only looking for a bit over 300RWHP and ~12-13psi, so the Pettit is a good choice IMO. Especially since it is just plug and play, and I wont need to drive somewhere to get it tuned. But I dont want to start an argument about that, I just want to know why my car wont start with this ECU.

 

You should take the cover off the ECU to ensure that there is indeed a "sisterboard" piggybacked onto the stock ECU motherboard. If you search enough, I think you might be able to find a photo of one somewhere. Not sure what the markings on the Pettit chip are.

If that checks out, not much else I can theorize other than you've been sold a fried ECU. Sorry.

 

Yeah, sounds like you bought a bad ECU...

Your '94 should have an EGR valve, but the '93 ECU (non-cali) doesn't care and wont even look for it. I'm pretty sure I have seen posts where people have used '93 ECU's in '94 FD's with no problems.

 

Yes I searched before purchasing it, and even asked the seller before I paid just to make sure there wouldnt be any complications between a '93 and '94.

 

if you plugged it in and it dosnt work,get your money back.

 

Thanks guys, Im talking to the seller now to see what we can work out, maybe it had been damaged in shipping....

 

Unless the ECU case had some major dents in it, that's highly unlikely. The motherboard and circuits are encased in resin, and it would take some serious abuse for the ECU to suffer damage in transit. I'd try to get your money back ASAP.

Basically, the ECU doesn't just "fail" for some trivial reason; it takes a serious electrical problem or someone messing with it internally for it to fail. I don't say this to point fingers, just stating facts.

 

Yes the box it was in did not appear damaged in any way, and the ECU was in packaging peanuts, so there is no visable damage. I have been in some UPS facilities though and they seriously do throw boxes across the room, so I suppose anything is possible. The seller seems to be very cooperative and from what I can tell is an upstanding guy, so Im trying to be as open-minded as I can. I just want to get my money back ASAP so that I can purchase another ECU.

 

Sorry im in the wrong thread but I have a question on a new Pettit ECU. For the same reasons Rxmfn7 bought this particular ECU, would a new one need to be programmed in any way? Or is it just completely plug in play, even with minor mods in mind for the future?

 

The ECU is already programmed. There is only one MAP used for their ECU's. It will support all bolt-on mods.

 

I opened up the casing today and inspected the boards for any signs of damage, or damaged components. Everything looks fine from what I can see, no components or solder joints appear damaged, all pins are straight, and there are no signs of damage to the casing. Ive been working in electronics for years and am an IPC certified inspector, so I know what Im doing. I wish I knew for sure that the ECUs were 100% compatable between '93 and '94, thats the only thing I can think the problem may be, unless there is something internally fried that was like that before shipping.

 

Is there anyone near you that can also try out the ECU in their car?

 

So you did see the Pettit sisterboard attached to the motherboard, correct?

Many people use different year ECUs with no issues other than the error codes for the EGR.

 

Yes, pettit board was there.

 

Find another 7 in your area, try it on their car. You'll find out if it's a bad ecu within 30min.