check engine light on

hi my check engine light came on today and i did the key on-off test and got the codes.......they were 0420 and 1684
0420 as near as i can tell is my catalyst seems to be inifficent , i dont no what this means.....
and code 1684 seems to be that the battery has been disconected within the last 50 starts ......... my ? about that is i have owned this car for 3 days and i bought it from a used car dealer DO YOU THINK THE DEALER NEW THIS AND JUST RESET THE LIGHT AND HOW CAN I TELL IF IT HAS BEEN RESET LATLY


TY DOUG.......:banghead:

I have a similar problem. How did you get those codes? I did the key on/off deal, and got 12 and 43, which mean:

Battery has been disconnected within last 50 key-on cycles (12)

Peak primary circuit current not achieved within maximum dwell time (could be on ignition coil #1, #2 or #3) (43)


The check engine light remains statically on when I'm braked or parked, and flickers when I start driving.



I don't know if this is related, but I've also run into the oil light flicker problem, which usually indicates a bad oil sensor. Eventually, it stopped flickering and just stays on all the time.