solved problem the hard way

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Doc1

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We had been to shrevport playing slots when the wife got lucky and had 3 machines pay off nicely. We decided to purchase a Miata and so went looking
We found what we thought was a nice used one and made the purchase with the agreement that they get a current inspection and registration for it which they did {we thought}
I We went this past july to get a new inspection and it would not pass.
Started looking and found the check light had been disconnected . WE connected it and it would not go out so started chasing error codes
After 9 months of tearing the dash out ,removing the seats ,the carpet the ,replacing O2 sensors pulling wiring harness apart looking for broke wire .
The culprit was finally found someone had installed the wrong ECM
This was never checked because the car ran fine and was showing codes
If you buy a used car insist on getting the paper work that goes with the inspection sticker that shows it passed .I understand that the law requires you to carry this in your car or at least in Texas. We did ask for it but was told it had to be sent to the state and then sent to us Well we know better now.
So even if you get a sticker get the paper second if it is a used car and codes pop up make sure they are for that car and not ghost codes.
The code I got was PO 141 BANK 1 SENSOR 2 HEATER MALFUNCTION
This is a real code for some cars but it does not exist in a 96 Miata so I was chasing something that did not exist.
When you get a code form a scanner even from an auto supply turn and call a dealer and see if the code exist. If there had really been a heater malfunction on BANK ONE SENSOR 2 it would have read PO1xx
All this time I had been chasing a problem that did not exist
We installed the ECM yesterday and bingo so far all is fine and dandy
 
What ECU was installed when you purchased teh car? Considering the 96 and 97 MY Miatas were the only OBDII NA's, I seriously doubt that there is any difference between the ECUs. Additionally, Mazda varies the ECU connectors from car to car so that it's almost impossible to swap computers between different models. Perhaps the computer was just faulty?
 
Why would you tear the car apart trying to fix the problem when you didn't even diagnose the problem at all.

Waste of time, energy, etc.
 
solving problem the hard way

Hello Pluto316,Kcbhiw,& Mazkid
Firts thanks Pluto for voting I should have left some things out but thought it would be interesting.
Kcbhiw There is a big difference in the 96 TO 97 ECM
The 96 calls for a BPS1-18-881 or you can use 881A
The 97 calls for a BP3A-18-881A
I had the BP3A tested and it is fine nothing wrong with it
The ECM IN a 96 does not monitor the rear O2 sensor heater the 97 does monitor it. You will get a p141 code of "heater malfunction bank 2 sensor 2
since it is not seeing it then the 97 Ecm keeps giving that code malfunction
The 97 will plug right in without any modification whatsoever
You can call Mazda and check for the correct one by using the VIN NUMBERS
Mazkid , not sure what you mean by not diagnose the problem. We did troubleshoot it from taking it to several places and having it checked to even buying a software package to monitor the sensors read codes and reset the CEL.
Everyone and even the books and software came up with the same code of a PO141 O2 rear heater malfunction ,Also TWO dealerships, a very highly touted Mazda repair center that is on the Net plus a few other folks .Told me that the problem had to be a broken or chaffed wire causing the heater to ground out which kept the CEL on {and they suggested taking the wiring and looking it over from steam to stern}
I have worked on cars for years and have a son that is pretty darn good auto mechanic ,He also has firend that is ASE CERTIFIED and it even got them as they agreed with everyone else ,believe me this was not a tinker here tinker there type approach . It was taken step by step and done what was suggested by a lot of people and as a last resort took the car and wire harness apart
No one even considered the ECM for the same reason that KCbhiw mentioned who would thought that they would innerchange and yet not work correctly
Hope this clears things up
 
Last edited:
Doc1 said:
Kcbhiw There is a big difference in the 96 TO 97 ECM
The 96 calls for a BPS1-18-881 or you can use 881A
The 97 calls for a BP3A-18-881A
I had the BP3A tested and it is fine nothing wrong with it
The ECM IN a 96 does not monitor the rear O2 sensor heater the 97 does monitor it. You will get a p141 code of "heater malfunction bank 2 sensor 2
since it is not seeing it then the 97 Ecm keeps giving that code malfunction

Ahh...gotcha. I learn something new every day.

Good post.
 
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