I am not intimately familiar with your vehicle but, I was
unaware that any vehicle of that vintage was using an O2
sensor after the catcon although many use a sensor for each
bank of a "V" type engine.  Are you sure this a a 1991 and
not a 2001 vehicle?  That said, has it occurred that the
sensors may have been warning of a condition that should
cause them to issue a warning?  You probably still have the
same problem that caused them to light up in the first
place.  When the CEL light is illuminated, it means that a
sensor has "sensed" an operational problem.  It was,
therefore, doing exactly what it was installed to do -
giving you an indication that a problem may exist.  From
there, someone has to follow up with a diagnostic process to
determine exactly what caused the sensor to issue a warning
signal.   What you need to do is have the ECM scanned for
fault codes and post them here along with any other
driveability or operation symptoms that may exist.  Many
auto parts stores now offer the scanning service at no
charge in the hopes that you will buy repair parts from
them.  Write down the exact code from the scanner along with
any descriptive messages from the scanner.   It is quite
likely that someone here has an appropriate answer for you
to assist in getting your vehicle repaired.

Lugnut

I don't know what a sensor light is.  There were two "sensors" in the
exaust, one before and one after the converter?  On a 1991 Isuzu 2.3
carb engine?  And it is a "V-4"?  I doubt much of this.

Toyota MDT in MO