re. Code 2111 - RPM Sensor

[Swann, Benjamin R. (BSWANN)]

I used to get this on occasion - typically associated with spirited driving
in the triple digit realm or finding the higher RPMs.  But occasionally it
would just appear.  I'd get the check engine light, run diags using onboard
mounted switch.  The code would usually clear and not re-appear until
sometime later, though with increasing frequency.

I noticed the connectors at the firewall where knock and the two sensors
are, seemed, well not perfect.  I labeled each one and inspected.  Not
finding any obvious problem, I cleaned the contacts and electrical taped up
the boots so they were sealed and looked new again.

I have not had any repeat of the code appearing.  I hope I didn't just jinx
myself by Pi$$ing off the AUDI Gods.

Ben
'87 5Kcstqw

[While checking codes today I got 2111, which according to SJM means:

2111 
RPM sensor
Open or short circuit,
Defective sensor & cables, metal fragments on flywheel teeth

Patient is a 1986 type 44QT manual. If anyone can help me with this, I
would greatly appreciate it. Thankyou 

P.S.   I hope it has nothing to do with metal on flywheel teeth.]