93 civic EX check engine light

My check engine light comes on when I accellerate up a hill. The garage said it might be the O2 sensor, but could not be for certain, charged me $50 for the diagnois. I changed the O2 sensor, and new fuel filter, still have the problem.

Is there a way to check the codes on this year model? It only comes on when I'm going up a hill with a steady increase on the accelerator. I went to Autozone, but they can only check for year models 1996 and newer.