[s-cars] RPM Sensor?

[Chris]

Folks,

Recently encountered a rough-running S6 w/ ~128k.  Most notable at idle/low
RPM but still there through the range. OBD indicated a #1 injector fault
(though when I pulled the injector connector while running, the condition
worsened & it tested good electrically so I presume it's fine..) but I
swapped it out w/ a known good one fr a fellow lister & cleared codes - ran
it w/ no change.  Now getting an 'RPM Sensor' (2111) code.. it also checks
out electrically (i.e. correct resistance..) any BTDTs on this one?  Do
these things fail?  Didn't see anything in the archives..  Any/all
suggestions appreciated - thanks!

Chris Hemberger
Amston, CT
95.5 S6 Avant
91 200q-20V Avant