Emission code P0420, Can someone please explain code to me?

A catalytic convertor problem. But not necessarily anything wrong with cat. The o2 sensors, one upstream (before) and one downstream (after) should read different before and after the cat. If they reads the same it triggers this fault code. See: http://www.obd-codes.com/p0420

If it is a sensor problem, there would be a separate code for which one is bad, right? Could converter be pluging up some how? Is there a way to test sensors?

Yes, in fact the cat converter could be partially plugged restricting exhaust flow, but you would notice a great deal of power loss. And it depends on the scanner, A cheap one will not. A professional-grade will. Yes, sensors can be tested. I need a minute.

http://www.ehow.com/how_5193043_test-sensor.html ...http://www.youtube.com/watch?v=7uqmYkl7t0c.....http://www.youtube.com/watch?v=7uqmYkl7t0c.....http://www.youtube.com/watch?v=QM2jO0_Cah0 ....You will need a good multi-meter

The best way to ruin a cat is to put leaded gas in it

There is a bank 1 code & a bank 2 code. What would be the difference between the two?

If the code is saying it is from bank 1, should I check everything real good from that side?

Is this the van?

You need to test or replace the 02 sensors on bank one. I don't know if they use heated sensors or not. A heated sensor makes the engine go in to closed loop sooner.(A whole 'nother story) Have you noticed power loss? ....click image to see it better The arrows are a bit confusing, they are pointing up to where the sensors are, not shown I will see if I can find an image of exactly where the upstream sensors are but I need to know, there are 3 available engines for 1999-- 3.9 , 5.2 and 5.9 Liter Even a better image than this drawing it's just an example ..a guide, not even your van

Hi everyone, thanks for everyones input! I have only 2 sensors, one before & one after cat. Yes that is the van we are talking about.I have a 5.2 engine. Sometimes lately the engine sputters or doesn't want to accellerate when I press on the gas pedal. I did change the cat 7 years ago, the ceramic insides collapsed plugging up the exhaust flow. Right now I don't feel a loss of power, just the smell of a rich gas mixture or unburned fuel.

Hi, I'm going to change both sensors & see what happens

Hi , I had to take the cat off to get to sensors, once off I checked cat out & the ceramic inside is gone. It is a hollow shell of metal. I guess we know what the problem is now. What do you think would cause ceramic part to dissintergrate?

Hi, the engine only has 88500 miles on it, changed cat 6 years ago, that one broke up & plugged the exhaust opening. The new cat had only 21000 on it.This one is still under warranty.

Hi Jim, I have been doing all the work on van. I did not know to do the procedure you just explained, but will make sure this time. Thanks, Tony

I got cat replaced under warranty, new sensors, & this is the recommended break in procedure for cat converter. This procedure come from Eastern Catalytic Converter website. Start engine, do not put foot on gas pedal! Idle engine for 5 minutes to slowly warm up converter. Then increase RPM to 2500 & hold there for 2 to 3 minutes.Turn off. Allow engine to fully cool down. Hope this helps someone, Tony

dont buy Dodge's problem, not fun.