Need dianogistic code description

[Randy Bindrup <bindy@flash.net>]

Hi All,
Driving home this afternoon, my '93-90CS's check engine light came on
and stayed on continuously.  Stopped and restarted the engine, light
went out for a few minutes only.  It doesn't 'feel' like anything is
wrong.  Pulled the codes and found a 23 and a 31 present.  Does any one
have a service manual that lists the codes?  I haven't obtained a manual
for this one yet, hoping it would be trouble free (har-har).  BTW, the
injectors and one cat was replaced at the dealer under warranty several
weeks ago.  It did run better after.  T.I.A.

Randy