Hey folks, my check engine light is on. I got the codes read and it was a P0420 code... Something about catalyst system efficiency for bank 1 is below threshold. Well I have the JTIS manual on cd and I input the code in and basically it was pointing to the catalyst monitor sensor (the O2 sensor after the cat) was faulty. So I replaced it with a BOSCH 15716 O2 sensor. A couple days later the light came back on. So I replaced the the other O2 sensor (before the cat) with a BOSCH 15717 O2 sensor and had the codes reset. Well, after a little driving, the light came back on. Now its spitting out two codes, the same P0420 code and now a P0133 code. I input the P0133 code and the JTIS manual points to the O2 sensor as the issue. The one I just replaced! Now I'm confused. Do you think it could be my cat converter? I hope not. It was replaced last November. Any ideas anyone?

 

So does anyone know what P0420 - "Catalytic effeciency below threshold..." REALLY mean?Is it a bad cat converter? Fuel filter? Help please.

 

I have the same codes. I took it into the dealer and they told me both catalytic converters are bad. I'm have not lost any performance and so I'm just living with it for now.

 

They said BOTH were bad!?! Wow! I was looking through the JTIS manual and it said that the catalyst monitor sensor on Bank 1 (the right side)was bad so I thought that it was just on one side not both. But like you said I haven't been having any performance problems either other than gas mileage so I'm just living with it also.Thanks for the info. How long have you had this problem?

 

I recently purchased my 2K 3.0 S-Type. It has 80K miles and shortly after purchasing it (maybe around 81K miles), I was getting the engine light. It now has 88K miles.

I did find some aftermarket cats that are universal fits. They require them to be welded on but they are relatively cheap. Here is one website: http://www.discountconverter.com/universal/index.cfm

So if I have to cross the bridge of cat replacment, I'm hoping I can find a local shop that can weld on one of these suckers at a reasonable cost.

 

Cool, thanks for the link. When I bought my S Type, the cat converter was already replaced with an aftermarket one last November. Thats pretty messed up to think that all it took was less than a year for it to go bad that fast. It was bought from davicomfg.com I guess they supposedly make good coverters. But I've recently noticed the car surging kind of like its missing. I was told that a vaccum leak,a missfireandan oil leak into the exhaust through the valve seals can cause this code to come up as well. So, I'm considering changing the coils and spark plugs on the passenger side bank (the one thats covered) and getting the car pressure tested for a vaccum leak, then see where that takes me.

 

Sounds good. Keep us posted esp. if you fixed the problem.