Volkswagen Repair: 2001 Jetta 2.0, fly by wire, jetta 2

Question
Hey, I have a 2001 Jetta GLS,63K miles, Automatic with a 2.0 AZG engine code. i recently replaced the transmission, but I'm still having problems, the car would suddenly downshift when i go over 70 MPH, before it did it at 55 MPH but i found out the speed sensor was broken...i replaced it. i was wondering since i got the tranny from a 2000 bug, with the same transmission code (fdf) do i need to get it programmed? and i also found out my ECU is defective...can you shed some light on all that? thanks alot

Answer
Hi Graham;
I don't mean to evade, but without being able to get a scan tool on your vehicle, I can't tell you if the ECM is having an emissions problem relating to your ECM defective statement.  However, your car may still be covered by a factory catalyst campaign.  I would call your local dealer to find out if an "Re-flash" is applicable, or if you can get a new catalyst, or both.  The FDF transmission has been used in Jetta's, Golf's, and Beetles since 1999, through 2003, or 2004, and in every different application, ie., engine, or body...(it was used in some 1.8T cars too)..there is different "coding" that controls the behavior in certain combinations.  If you have not "re-coded" the transmission to the specific application, using a VAGCOM, and laptop, or VAS 5052, or 5051, or 51B, then you have a transmission asking questions relating to load, that it cannot answer.  Especially if the transmission was originally hooked up to an AEG engine...ie., one with a throttle cable.  Yours doesn't have a throttle cable, just a throttle body with "fly by wire" hookup to your accelerator.