4 set 0116 B-12 Chemtool Carburetor, Fuel System and Injector Cleaner, 15 Ounce, (Single Unit)

My Honda is 15 years old with over 200K miles. and I get the dreaded Check Engine light with code P0402 (Cat code out of spec). You can either replace the O2 sensor or pour a can of B12 in the tank. One is $80 and the other $4. Both keep the light out for several months.Try this 1st before you have a mechanic change you cat or O2 sensor!