it seems there's a lot of immobilizer switch problems around.
My 2 cents, go to the nearest audi workshop and have the check with the VAG COM. highly likely its the immobilizer switch. Just replace them and u are good to go. i got mine replaced a few weeks ago after a heart stopping incident when i couldnt get my car started when ferrying my boss to a meeting!!
but, sometimes, the problem do crop up. usually happen when i cdnt start my car instantly and i depressed the accelerator pedal too long/too much during starting. when it happens, just turn off everything, take the keys out, pray, and start the car normally. usually solve the problem for me (after changing the immobilizer ignition switch).
btw, if u depress ur accelerator pedal when turning the ignition key (before starter) u are actually resetting ur TCU! of course, let go the pedal when starting the engine.
rizal
1996 A4 1.8 NA
p/s : help me find a manual gbox for my audi, please?