Last week I swapped my 94 hatch with a b18b1. Everything was fine and I didn't have not one cel. The other day I had to tap a thread for one of the holes in the tranny but my header was in the way so I took it off and it was kinda hanging by the o2 sensor. When I was done, put the header back on and I got a check engine light. Today I pulled the code and it was a code 41. I think thats a primary o2 sensor heater. What does mean? What needs to be fixed or checked? I know if its a code 1 my o2 is bad, but what does it mean by heater? Thanks for any help.