[V6-12v] Trouble code 2331

[Ron & Janet Frazier]

I have a 1993 100cs wagon and I have pulled the 2331 trouble code when 
the check engine light came on.  I believe this code is for one of the 
O2 sensors.  5 years ago the same thing happened.  they replaced both 
o2 sensors and that didnot solve the problem.  They did a smoke test 
and then replace the throttle body gaskets and the egr vale gasket.  
Does anyone want to venture a guess as to what is really wrong with my 
car this time.  Replacing gaskets is cheaper than O2 sensors.  The 
problem is knowing which ones without a smoke machine.  Does anyone 
have any guidance.  also, do I remember correctly that trouble codes 
are cleared one you start and operate the car after the previous 
occurrence.

Ron Frazier