I understand the software for this PCM to be in a OTP EEPROM. Is the coding also in there? I tried to recode with WSC 65535 and also with whatever VCDS uses for the ABS, neither one worked. Is recoding a matter of getting the right login code (I tried a few others I found here and there, also did not work) or will I need to resolder and reflash before I can recode?

I want to recode the PCM to match the TCM. This is actually a photo of my spare PCM, which is from a 1998. My car is a 1997. This PCM also came from an A8 and thus had the "correct" coding in it already when I got it. I want to change 01... to 04... since my TCM is coded 00011.

Since coding my TCM to 00011 (rest-of-world no dsp ... http://www.audipages.com/Tech_Articles/auto_transmission/codingtransmission.html) I have intermittent 18020 PCM incorrectly coded. It doesn't light the MIL. Is that just a coincidence? I read that 04xxx and 05xxx are EU, 08xxx is China and 25xxx is Japan.

What the docs say about a 18020 is to set the coding correctly because incorrect coding may affect emissions, etc. Oh, you don't say? Then there's a coding table which, aside from what I've typed above, agrees with what you said. I take it at least USDM and rest-of-world have different part numbers, then? And the easiest thing to do is just get a PCM from wherever I want the coding to be from? Assuming that's even relevant.

OK, but clearly there is such thing as an A8 PCM similar to this one which will take those codings. Could you address my second paragraph please? Or anything else I said?