I have a 2002 S4 2.7 TT and I don't like the way it drives and figured I would fix that by reflashing the ECU.
I got myself this cable: https://www.ebay.com/itm/FTDI-FT232RL-VAG-COM-KKL-409-1-OBD2-K-LINE-ISO9141-USB-FOR-VW-AUDI-SKODA-SEAT/141651292396?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
and downloaded a copy of the nefmoto software.
Software will read ECU info just fine and read DTCs also, but when I try to read ECU flash it reports a security problem. The ECU does go into boot mode (or at least the engine running firmware stops, as evident by the check engine lamp and EPC lamp turning off and engine becoming un-startable until the key is switched off and back on.


Some observations:
The software usually stays at "Negotiating communication timings" forever after it first reports security access was rejected, only if I turn the key off and back on or hit cancel current operation will it exit that state and report that the operation failed.
There are some unprintable characters in the console at the end of this line: KWP1281 connect info: 8D0907551T  2.7l V6/5VT

Is this a known issue or am I doing something wrong?
Is this an indication that some dumbass has flashed the ECU before and locked it?
What tools will I need to perform a bench flash and bypass this boot loader that is obviously not cooperating?

I've had the same problem with stalling at negotiating communication timing on my B6.

Solution for me is to change the baudrate dropdown to 38400 immediately prior to reading or flashing. If you connect with 38400 it will revert to 124800 as soon as it communicates, so change the baud after that initial connection.

I don't know why it seems to work, but it does. It only adds a minute and a half to a full read/flash so I live with it. Give it a go...

Well that worked a treat. Dropping the baud rate to 38400 and I performed what looks like a successful read. Compared with virgin bin downloaded from the forum to verify that it's a good read and that my ECU is stock.
According to the NM flash read utility, my ECU is of 8D0907551T type and I have found only one Tunerpro definition file for that which is very incomplete, with only about 30 of the several hundred tuneable parameters defined.
What I would like to know is if any other bin is interchangeable with this hardware, or if someone has a more complete definition available for my current bin and is willing to share/sell. Or maybe just supply a modified file, what I mostly need is a few DTC checks disabled, because I don't want the CEL lit constantly due to faults which are not of any concern such as evap and catalysts, and I want the super lazy throttle response fixed so the car is less annoying to drive.

OK, so I can just grab a stock 551M bin and tune from there?
Any changes needed just to cover the change from T to M?
I see there are two stock 551M bins in the repository labelled 0001 and 0002, is either one a better starting point than the other?