In the past six months I've replaced the plugs, coils, air filter element, and both O2 sensors on my 2000 V70 XC. The car is running very smooth and strong and seems like it will go forever. However, just yesterday, I got the P0422 OBDII code. I know this means the cat is reporting a problem.

I'm wondering if others are seeing cat failures at about 100K miles or is this premature? I've heard the cat is very expensive to replace from the dealer. I know there are places that rebuild cats. I wonder if anyone has tried such a service with successful results? There are also aftermarket units that are much cheaper than stock but I don't want to find out the hard way if there are any incompatibility issues with them.

Stuck between a cat and a hard place. What to do?

RGW.

How is your fuel economy? Is the car running rich?

This link (pg 10) has some info supporting the idea not to automatically replace a cat for an efficiency code without doing some additional checks.

http://www.epa.state.il.us/air/vim/air-repair/air-repair-review-06.pdf

If there is a vac leak, marginal O2 sensor, dirty MAF sensor, etc. then as Klaus says, the mixture can be a little off. For these reasons or if there was a previous history of misfires, etc., the cat can become contaminated. If the original problem gets fixed the cat could possibly clean itself out after extended driving. I had this happen. After a year or so though the code is back. I'm now looking for other reasons not to replace the cat.

Some cheap aftermarket replacement cats aren't good enough at the outset to guarantee no efficiency codes will appear.

Good luck...

P0422 = Main Catalyst Below Threshold (Bank 1)

The front O2 sensor has a problem. NOT the cat! Cats cannot be rebuilt. You could spend a lot of money putting on a new cat with O2 sensors, or you could just send me the cash :) I could always use an extra grand!

Before you spend mega bucks, you need to determine if it is indeed the O2 sensor gone bad (which I doubt) or one of the many vacuum hoses that is leaking and allowing outside air to enter the system. Also, when was the last time you had a tune up? Plugs do make a difference in how much fuel is being burned.

Klaus

I replaced the plugs and coils about 500 miles ago. The car is really running great these days so I don't suspect that. I also have new O2 sensors which have worked great up to now. I cleared the code and still haven't seen the light pop up in the last 100 miles. However, I suspect it will trigger again in the next couple of weeks -- as the CEL often does.

A vacuum leak is the most likely cause. The car is only 7 years old so I would be surprised if it has cracked hoses already. I wonder what hose(s) I should look for? Is there anything on the web that identifies the places to look?

Thanks,

RGW

Check around the intake manifold first. The worst offender is usually the one coming out of the manifold on the passenger side. It is also the hardest one to replace!!!
Also check below the battery area. I just remove the air guide/splash pan and look up.

Klaus
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Please answer your responses. We need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)