My girlfriends 97 Accord thru a PO420 code which translates to Catalyst System Efficiency Below Threshold. I was told it was bank 1, what the heck do they mean by bank 1? Thanks in advance.

 

Your girlfriend's accord must be a V-6 in order to have bank 1 and bank 2 which relates to the left side or the right side of the engine (3 cylinders per bank).

Typically if you took care of the car and your exhaust doesn't smell funny then the O2 sensors may be giving a false reading to indicate that your convertor is not operating efficiently.

The cheap and non diagnosis way would be to put in (4) O2 sensors by yourself since the car is over 10 years old and the O2 sensors are probably not working properly at this time and will trip a code as you have mentioned.

Good Luck and post your results....