Is there really a difference in OEM vs. aftermarket parts anymore?

[inline 6]

No mater what we are talking about I buy OEM unless there just isn't an option or there is a clear upgrade. I've been burnt too many times by cheaper parts that were supposed to do the same job.

[Gasser64]

With a p0420 I would say it needs a cat.

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Have only had 0420 be a cat. I would check your manufacturers emissions warranty.

Went back and read this thread again, and this time paid more attention lol.

And it reminded me of this. I had a 2003 altima and they are both nissan and share the same codes. It too had the P0420 code, and when I took the exhaust off looking for the problem, all the cats guts came spilling out when I tipped all the tubing up on its end. I'd say its a 99% you have a dead cat. If you are able to, just take the exhaust off, and shine your light down in there. Or do like I did, and get it all the way off of there and tip it up and maybe bounce it off the ground a bit. You'll probably have some cat chunks come out of there.

The reason I ended up having to do this, is because the car was running fine, and then suddenly not so great, and it threw that code. The chunks had ended up making a clog. Yours may do it too, eventually.

[4king]

P0420 usually indicates the rear oxygen sensor has detected not enough air flow past the sensor in the exhaust.

Many times this is incorrectly diagnosed as a catalytic converter when it can be as simple as a crack in the exhaust before the secondary oxygen sensor.

As mentioned the government mandates an 8 year 80k warranty on catalytic converter equipment. My wife's 2001 trans am received a new catalytic converter free of cost in 2007 .

Oxygen sensors I would buy from auto parts stores, however there are things that aftermarket suppliers simply can not clone correctly.

More than any other part I see motor mounts that are way off in their dimensions or even bolt patterns. Some parts suffer from their original molds deforming over time, or just poor clones.

You should never skimp costs and purchase major engine components such as timing tensioners or guides from any autoparts stores.

Your basic stuff is going to be just fine from anywhere, but yes the dealer often marks up prices

[mikeb]

"the sensors will need replacing too if they can't get them out"

How do they replace them if they can't get them out?

In my experience a quick hit with a flame wrench usually gets stuff to come out