I have been trying to start my freshly swapped JDM 13bt for 3 months, but have been unsuccessful. So, I brought it to a shop yesterday to have them look at it. They told me I had no spark (which I had checked and am sure that I did, but whatever). So, they pull the ecu out and open it up and what do they find??? The insides looks like it had been sitting in water for months. Also, a few diodes were blown. I bought this ecu from a kid in my area who told me it was in perfect working order. Now that SOB doesn't want to give me my money back. The thing with this ecu is that it was tuned, 15 psi of boost, redone fuel maps, no fuel cut, etc. Oh well.

Question:
Could I use a USDM ecu on my JDM engine and engine harness?

 

As long as the wiring harness and ECU are from the same series, IE both s5 and both s4.

 

ahh, cool thank you very much.

 

Why did you use the JDM harness? You could've saved yourself a lot of work by leaving the original harness where it was.

I wouldn't be too worried about not be able use that ECU. I wouldn't trust a "chipped" ECU at all unless I knew exactly what had been done and by who. You have no idea what's really been done to it, and given how difficult it is to properly retune old Mazda ECU's I'd be wary of the claimed changes you listed.

 

the harness came with the engine. and that was my bad on the ecu. I should have checked it out before I gave him the money. oh well.

 

That is not entierly correct. Some Zenkie FC's in Japan used the CAS sensor as part of the emissions harness and not the body harness as USDM ones used. So it is a shot in the dark if you did not recive a clip or a matching emissions harness and ECU from the car.