I have a '04 GS300 and have a PO430 CEL code stretching back from last winter. Typically this code means you have bad O2 sensor(s), bad or failing cats, or perhaps an exhaust leak. I took the car to a muffler shop to have it checked for leaks and none were found. The guy said that catalytic converter is bad and needed replacing. That same day I took it to the dealer and they too said the cats were bad. So I decided to finally have both my O2 sensors replaced on the bank 2 side with OEM Denso sensors. CEL was gone but after about 30 miles of driving it reappeared again. Now I'm convinced that it is indeed the cats which as folks know is a very pricey part to replace. I'm still on the fence on getting the OEM or aftermarket cat. I don't see a lot of evidence on the forums that people with my model vehicle have gone with aftermarket cats. Actually on one post someone had mentioned that aftermarket cats do not last as along and you will be doing the same thing all over again in a shorter time period. I do not see any proof that supports that claim. I see that Magnaflow has cats for our cars selling for around $659 while another company has cats for about $500. The OEM cats market for about $1200. I have no problems with some aftermarket parts since my car is loaded with them. But coming from a maintenance perspective and given the pricey amount of this part, would going aftermarket be a good decision?

-G

 

I would just get an O2 simulator and be done with it.

 

I have a Magnaflow cat on my RX300 (and it is larger than the cat that was on it) and no issues.

 

No issues with aftermarket cats on any of my other vehicles. You can try drilling a sparkplug anti-fouler and installing with your downstream o2 sensor to try to eliminate the code. Here's a pic as an example on another car.

 

I never heard of an O2 Simulator/Spacer until I saw the responses in this thread and I've since researched the hell out it. I decided to order one knowing now that my cats are most likely bad and I'll probably will be polluting the air more due to the increased emissions. It won't too bad since I do not daily my car. My plan is too at least past inspection and perform priority maintenance such as changing my timing belt, water pump and spark plugs. This is work that should be done around 90K and I'm at 112K now. I rather drive around with the bad cats for a few months than drive around with an aging timing belt and risk serious engine damage. Eventually I will get the cats replaced and hopeful others chime in with their experience with aftermarket cats.

 

before anything, try getting your cats nice and hot by doing a long sustained highway drive or where possible after getting fully up to temp..several sustained high acceleration blasts till your exhaust is stinking behind you. If a cat is clogged, it is from not being heated enough.

 

I also have the code saying that I have bad cats. Says that Bank 1 cat is bad.

What will happen if I dont replace the cat and continue my daily driving?

I dont have an emmissions test for 1 more year.

Will I do serious damage to the motor or will the car just stop working?

I see that this is an expensive part to replace and I'd rather put it off for a year if I can. But his is my daily driver and I put 20,000 miles on it a year.

Thanks.

 

I decided to go with the O2 spacer/simulator and ended up passing inspection. It installed easily in the downstream 02 sensor location. This is just a short-term fix though.

 

It depends. If you were like me and had just the one code such as PO420 or PO430 then the car will not suffer. My car still drove fine and I had no lean so there were no adverse effects. The only problem is that the catalytic converter was not properly doing it's job so it'll be emitting more pollutants in the air. I don't daily my car so I'm not concerned about that at the moment.

 

if you have an infrared heat gun you can measure the temp of inlet of cat and at outlet. Outlet temp will be hotter if it’s working