sal346

every now and then my SES light will come on for a few days then shut off for a for a month or so then come back again, i hooked up and obd 2 scan tool to my car and scan for codes it had a record of a code P0420 which it said was a "low catalyst efficiency bank 1", does this mean one of my cats is bad or that my o2 sensors are malfunctioning? or is it something else? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> the only mods i have to my car are a lid and corsa catback, but i couldnt see either of these causing a trouble code for the catalytic converters. any info would be greatly appreciated, thanks

sal346

thanks for the advice jay, ill try that the next time its nice outside, the weather really sucks around here right now, either way i still have a warranty on the o2 sensors and cats so if they're bad ill just get a new one from the dealer <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

jaywoo

I'd swap the two rear O2 sensors around. If it comes back as a P0410, then you know it is a bad O2 sensor. If it stays the P0420, then it may be a bad cat.