Code #P0421. Please help.
 

Guys,

My check engine light came on; Code #P0421: Warm up catalyst below threshold (Bank 1).

What does it really mean?

Thanks,
John

Your Catalitic converter took a crap...

Try checking the O2 sensor but, I'm pretty sure is the cat.

The O2 sensors and cat were replaced at 40K miles. The car currently has 108K.

Do you really think its the cat? Is there a DIY on how to test both?

Appreciate the help.

I couldn't really find any. The only way I know to test if it is the sensor is to get a new one, and those are expensive on their own. Can you see if you Cat is glowing red? if it is then is probably the cat and not the sensor and viceversa.

Guys,

The cat should have a foul smell such as rotten egg if clogged right? Well, there is no smell at all.

Can it be the O2 sensor is the culprit?

Is Bank 1 in the passenger side?

Thanks guys!

Not all the times they emit that smell, this is actually the first time of someone mentioning that. But I still wouldn't discard it, the O2 sensor is cheaper so I'd go that route too. As far as I know Bank one is the passenger side if you're in America, the driver side if in Europe or Asia.

Thanks Dan.

This maybe a stupid question guys, but which O2 sensor? Is it after or before catalyst?

Also, just to verify that the O2 sensor I'm going to buy is the passenger side (Bank 1).

Thanks guys,
John

If I'm not mistaking this should be the one after.

Thanks Dan.

Can someone confirm this please before I spend over a 100 bux O2 sensor.