a6 airbag light on (and then off briefly, and then on again)
 

hi,
i live in cambridge, MA, and have recently bought a 99 a6 quattro
avant, which now has 82K on it.

last week i had the airbag light come up, and brought it in to my local
mechanic in cambridge, mass., to get it diagnosed. he diagnosed it and
come up with the code for 'bad passenger airbag, resistance is too
high' (i believe it was 0589 on his computer). so, he tried to clean up
the wiring, and voila' THE LIGHT WENT AWAY. he called me to pick up the
car, but when he took it for a test drive, the light came up again.
this morning we diagnosed it together and he showed me that the
successive steps for that error code are, in sequence: clean up/check
the wiring, replace the passenger airbag (part is $1,200), then
eventually the control module (part is about $600).

i am confused:

- IF THE LIGHT WENT AWAY, even momentarily, shouldn't it be related to
a false contact and the such, rather than to something major like the
airbag gone bad?

- i read all the postings related to 'airbag light' and the range of
responses is wide: they go from tough luck, to AUDI will replace it
even if out of warranty, to reset using VAG-COM or the like. could
anybody shed some light on the situation i illustrated above?

- last, why do i need to replace the airbag before the module? in doing
so, don't i risk to replace a good airbag (if the problem was indeed in
them odule)?

thanks in advance!
fabio