2001-2005 PCM modification ?
 

I did something a little ill-advised and am trying to get an OEM engine swap through CARB. The receiver car is a federal emissions 1991 BRG. The donor car was a federal emissions 2005, except for the PCM. I got that off of EBAY from another federal emissions 2005 (I did not get the dash with the donor car, and that meant no immobilizer.)

Here is the issue: they want me to prove the PCM is unmodified. I have taken it to a dealer, had the codes read, and received a print out of everything they can pull off of it. But that does not really show that it is not modified. I know the newer cars can have the PCM reflashed.

The question is if the 2001-2005 series can be modified without physically replacing chips? I know the clock chip can be replaced, but that breaks OBDII comms. I know you can send some year model PCMs out for reprogramming, but IIRC they replace a chip to do that.

Thanks

That does sound a little weird to me. Isn't it on them to prove that it is modified instead? How can YOU prove that it is not modified? And no, the 01-05 ECU can't be flashed as-is. It needs to be modified to be reflashable, with obvious tell-tale signs on the board.

Ask them how to prove a negative.

Unfortunately it is up to me to prove and document everything. I am lucky that my 91 is a federal car. I have not seen a California PCM for sale that was not an automatic. (I do have one here but it is missing the immobilizer.) Proving the PCM is stock is harder than I thought. Those years don't return a VIN on the OBDII check. I have paid to have 3 different cars tested (at $150 each) to see if a different part number PCM would return a VIN. After that, the Mazda tech told me that they could not get the VIN from the PCM over OBDII for anti-theft purposes.

It has been a learning experience. I had an aftermarket (CARB compliant) CAT in the car, but the O2 sensor was not in the stock location. Fail. Purchased brand new OEM NB midpipe for car. Lots of $$$ thrown at this.

Buy a new PCM from Mazda? But seriously, ask them what the burden of proof is to show it is unmodified.

Since it's they who demand proof it seems reasonable to expect they can tell you what proof would satisfy them.

I guess if it was for my own peace of mind, if I suspected a device might have been modified, I would examine the circuit board to see if any of the soldering had been reworked.

I would offer them a combination of whatever documentation you have from the purchase, showing you ordered a normal ECU and not a special modified one, plus the Mazda dealer's reporting that the ECU behaves just like a standard one, plus a couple of nice, detailed photos showing the original factory soldering undisturbed on the board. That surely ought to persuade any reasonable person.

<eta> Just saw that this post is weeks old - oops - did you resolve the problem?

They accepted it as an OEM PCM. They are not happy with the fact that they can't read the VIN from it. I also took it a certified testing station for a code read to prove it was ready (something they required before they would let me make another appointment) and none of their newer scan tools would even connect to it without the VIN.

Thought I had it done last week, but it triggered a pending P0441 (EVAP blocked) on the drive to the test. We did not even bother to test it. I have since replaced all the EVAP system and am driving to get it ready. Once it says it is ready, I will try to recreate the drive to the test center and see if something unrelated to the EVAP system caused the fault. For instance, I had the lights on during the drive (light rain and I was playing it safe.) I very rarely drive with the lights on. Like close to never.

To top it off, the differential is dying. I am really tired of this car now. And to add to the fun, my hybrid Camry needs a new battery pack. It quit running on my drive home yesterday.

When I spoke with a CARB ref about doing an LFX swap, he basically told me that I was SOL unless the VIN on the ECU matched the VIN on the engine. He also said the way to prove that the ECU was unmodified was with a letter from a dealership stating such. This essentially echoes the post here: https://www.miataturbo.net/build-thr...2/#post1408175

I'm kinda surprised you got through without being able to read a VIN. I'm guessing the age of the donor has something to do with it.

So are you now "just" stuck on getting that whatever's causing that code fixed?

I got the statement from the dealership. They told me that they can't get a VIN from a PCM that old. And the ref accepted it.

I had a test in mid May. The day before the test my ABS light came on. In my troubleshooting the ABS light, I pulled the room (PCM +12v constant) fuse and reset it. It has passed all of their scrutinizing except for the PCM being "ready" and code free. Once I prove that it will be legal.