[V8] Flashing CAT light

[Richard Hill]

Hi Audifans,
   The last 2 weeks my ''80 V8Q has been flashing the red CAT light,
awful annoying.  What is the solution ? Change O2 sensor ?
Is this the wrong place to post abouy a sick Audi 90 w/ bad auto-trans ?
 
Rick in UP MI 
 
( I'm my own Audi Club )
2 V8Q's
"91 Audi 100Q
"88 5000 TQ
2 "87Q's
"94 Audi 90  ** NEEDS  AUTO-TRANS  OR PARTS TO REBUILD  any sources out there for tranny rebuild info ?
"93 Silverado