Catalyst question

[VicRod74]

I was wondering if any of you mechanics out there could help me out. So the catalyst converter for my Toyota Camry was replaced with an aftermarket converter, cuz the original one went rusty and it had a hole on it. Anyway, after a month I'm now getting the check engine light. A friend of mine who has an ODB II code reader checked it out and it reads P0420. So I googled this on the web and their saying that the catalyst is at fault. But how can this be it's a brand new aftermarket catalyst? The other option is to check the oxygen sensors. So i'm not sure what to do, cuz a brand new OEM catalyst is expensive.

[PMoth]

Unless your friend has one of the more expensive code readers, I would take your car to Autozone and let them scan it for free. o2 sensors can range between 50-150 bucks on those cars so it helps to know what the problem is before pissing away money. Again, Autozone does this for free because many customers actually end up purchasing replacement parts form them.

[nautica2o3]

What year is your Camry? I think Toyota has a 8 year or 80,000 mile warranty on emissions equipment. Anyways, a faulty secondary O2 sensor will also say a good working catalytic converter is bad.

[xXCriticizeXx]

or the newer cat flows more air and the sensor is programmed to the stock cat so its reading slightly higher emissions levels and throwing the code.

[VicRod74]

It's a 97 Camry V6. The warranty has already expired The fuel is also running a little rich, the exhaust smells a little funny.

[PMoth]

It's a 97 Camry V6. The warranty has already expired The fuel is also running a little rich, the exhaust smells a little funny.

It could very well be that your o2 sensor has expired. Again, I would go to Autozone and let them scan it for free. Then, take it from there.

[TSi+WRX]

^ Check out the post-cat O2 sensor.

But.....

or the newer cat flows more air and the sensor is programmed to the stock cat so its reading slightly higher emissions levels and throwing the code.

This is also very, very likely.

If your rear O2 sensor is fine, you can try drilling out (a standard hand-drill will do, just use plenty of WD-40 as cutting lube) "spark plug defoulers" or "spark plug anti-foulers," (just ask for this by-name, the store clerks at a place like AutZone will know exactly what you're talking about) and using them to "space out" the distance between your post-cat O2 sensor.

If this is the case, then it's usually a trial-and-error until you get it right. Start with the shortest length of spark plug antifouler, and to then play with the length/stacking of additional units.

What you're doing is essentially removing the post-cat O2 farther from the main exhaust stream, thus allowing it to "see" that your new cat is still working properly.

Common trick on vehicles where one or more cats have been removed (or replaced with freer-flowing one[s]), for various reasons.

This trick should not significantly affect any other vehicle operating parameters.

Be sure to liberally coat the threads with anti-sieze. These things are usually made of metals that are not corrosion-resistant.

[lugnuts]

couldn't he just put in an O2 simulator in?

[TSi+WRX]

^ That should work, too!

[ELVATO]

I'd replace the O2 sensors. From a 97 car, they're probably due anyways. It happened to someone with an older F150 who replaced their cats with high flow cats. They CEL kept on coming on. They replaced their O2 sensors, and problem solved. It seems the old O2 sensors "didn't like" the increased flow.