[kevinbahnz]

Just bought a scanner tool and those 2 codes came up. Can anyone explain what these does mean and how to fix them or do I still have to bring it into my trusty dealership to further diagnose the problem. If i can remember correctly the dealer replaced one of the O2 sensors back in September of 2011. Can this be another sensor gone bad?
6/8/12- Been driving around for a week with the SES light on and had an Indy shop replace my oil filter housing gasket ($200). The old gasket still looked new except that it was broken in one place. Anyways went to pick it up and drove it back home(about 30 miles) and the SES light disappeared. It could be about a million things that could contribute to these codes right? I just hope it doesn't come back on.

[queensfield]

So, these codes are saying that the catalyst efficiency is below threshold for banks 1 and 2. ECU determines this by comparing the oxygen sensor signals before and after the catalytic converters. It is likely that the precatalyst oxygen sensors have gone bad. They are due at 120K miles. If the dealer replaced precatalyst sensor for cylinders 1-3, then replace the one for cylinders 4-6 or vice versa. Hope it is not your catalyst converter- they usually last a long time, unless there was a misfire and the cat got flooded with unburned gas. Cats are very expensive.

[Chuck]

If you have both codes, the computer is flagging both bank's cats. Are you running catless downpipes (gotta start with the obvious question)? If not, and you have not had a major misfire issue, oil consumption or blown head gasket (each can kill a cat), I would suspect something that would equally affect both cats such as a skewed air mass meter or unmetered air leak. I would suggest taking it somewhere to have it properly diagnosed, but the cats should be covered at least 8 years/80,000 miles under the federal emissions warranty through the dealer so long as they can't prove modding caused the failure.

[kevinbahnz]

Thanks for the input. My car is a stock 2008 335 @ 90k miles. i think they replaced one of the sensors @ around 70k miles. I'll have to swing by the dealer and ask them which one they had replaced.

[kevinbahnz]

Update, replaced 3 O2 sensors and car is fine now..