Help with cel P0420.. Searched but no answers

[yung911]

Hello!

I'm fairly new to renntech.org. I usually use this site to get most of my information on my 2002 996. Well, my car has a K&N intake, rss plenum, and evoms exhaust. When i first installed the K&N, i would get a CEL every-so-often. However, this time it's giving me a P0420 fault code. This was not the same code that was popping up before (i don't think).

I checked under the OBDII section on what this means:

P0420 Catalytic Converter Conversion Too Low (Cylinders 1 - 3)

What does this imply? Is my Catalytic converter bad? Or do i need to change the spark plugs?

What gives?

Thanks in Advance

Bao

Edited August 2, 2007 by yung911

[Loren]

P0420 TWC conversion, bank 1 - above limit

Possible fault cause

- Oxygen sensor ahead of and after TWC exchanged

- Valve lift fault

- Aged oxygen sensor after TWC

- TWC faulty

[PTEC]

This fault almost always means a dying cat. You can try switching your oxygen sensors from side to side and seeing if the fault changes but Im guessing you've got a dying cat. If you live in the US I believe cats are covered for 8 years 80,000 miles under the federal emissions warranty.

[yung911]

thanks guys for the response. I'll ask the dealer about that federal emissions warranty law. But will try switching the o2 sensors to see if that is the problem first.

Bao

[deputydog95]

I've got codes P420 and P430, combined with a rattle in my exhaust. I am running muffler bypasses so the rattle must be in my cats. My indy tech banged on the driver side cat some and thought he heard some element rattling around in there.

Are my cats probably deceased at this point?

[Loren]

I've got codes P420 and P430, combined with a rattle in my exhaust. I am running muffler bypasses so the rattle must be in my cats. My indy tech banged on the driver side cat some and thought he heard some element rattling around in there.

Are my cats probably deceased at this point?

You should look at the O2 sensor and graph the voltages. Could be worn out (aged) after-cat sensors.

Usually you see a bad or bad sensor on one side - not both at the same time. All the more reason to see what the O2 sensors are doing.

[PTEC]

I've got codes P420 and P430, combined with a rattle in my exhaust. I am running muffler bypasses so the rattle must be in my cats. My indy tech banged on the driver side cat some and thought he heard some element rattling around in there.

Are my cats probably deceased at this point?

The cats coming apart is fairly common on these cars, though I dont know if I've ever seen both come apart on the same car (which is what your faults indicate.) I've seen plenty of P0420 and its always the cats. When they do come apart is a pretty nice knocking sound coming right from the cats. Removing them isn't that hard if you have access to a lift or some good jackstands and its usually obvious if one has came apart if you get if off the car. Like I mentioned earlier see if you would apply for federal emissions warranty, which is 8 years or 80k miles in CA and 7 years or 70k miles everywhere else.

Edited January 6, 2009 by PTEC

[fotostars]

Just got the same problem. I plotted the O2 sensors before and after the cat on both banks using Durametric.

See below graphs:

My analysis:

Bank 1 has the post sensor oscillating nicely following what the pre sensor measures. The Cat must definitely be shot!

For Bank 2, it's more like what I expected, only that the value of the post is pretty high. I was hoping to see it stable around 0.45V?

Anybody can give me some feedback and an educated analysis of the graphs

Am I right? Do I just have a bad cat on Bank 1 and sensors are fine?

It is with the Engine at Idle after a 10min drive (so warm everything)....

Thanks!

Rich.

PS: It is on a US 996 C4S 2002 , 6 spd with 39K miles and quiet a few track days in the past 6 months... :-)

Edited February 26, 2009 by fotostars

[summoboy]

HEY DEPUTYDOG95. I have some spare cats from my 05 997s - if you need any. they are in very good shape and do not rattle.

[PTEC]

Just got the same problem. I plotted the O2 sensors before and after the cat on both banks using Durametric.

See below graphs:

My analysis:

Bank 1 has the post sensor oscillating nicely following what the pre sensor measures. The Cat must definitely be shot!

For Bank 2, it's more like what I expected, only that the value of the post is pretty high. I was hoping to see it stable around 0.45V?

Anybody can give me some feedback and an educated analysis of the graphs

Am I right? Do I just have a bad cat on Bank 1 and sensors are fine?

It is with the Engine at Idle after a 10min drive (so warm everything)....

Thanks!

Rich.

PS: It is on a US 996 C4S 2002 , 6 spd with 39K miles and quiet a few track days in the past 6 months... :-)

Yeah your bank 1 cat is totally shot. Check out the graph for bank 2. See how the red line (indicating o2 sensor after cat) is nice and flat. This mean your cat is working and oxidizing the exhaust gasses. Notice how the graph for bank 1 the lines are almost the same. This means the o2 sensor in front of the cat and behind the cat are reading almost the exact same thing. AKA... your cat isnt doing jack ****.

Edited February 27, 2009 by PTEC

[Steve Danielson]

What settings do you pick in durametric to track these oxygen sensor value? There are a couple of categories of O2 values and I'm not sure which one. Also did you have to take screenshots or does the tool automatically save logs of your values? I am troubleshooting a P430 and this would be very helpful.

Thanks!

Steve

Eidt: oh wow this is an old thread :)

Just got the same problem. I plotted the O2 sensors before and after the cat on both banks using Durametric.See below graphs:My analysis:Bank 1 has the post sensor oscillating nicely following what the pre sensor measures. The Cat must definitely be shot!For Bank 2, it's more like what I expected, only that the value of the post is pretty high. I was hoping to see it stable around 0.45V?Anybody can give me some feedback and an educated analysis of the graphsAm I right? Do I just have a bad cat on Bank 1 and sensors are fine?It is with the Engine at Idle after a 10min drive (so warm everything)....Thanks!Rich.PS: It is on a US 996 C4S 2002 , 6 spd with 39K miles and quiet a few track days in the past 6 months... :-)

Edited March 4, 2013 by Steve Danielson

[Silver_TT]

_Steve,

_{You would want to look at 4 values:}

_{O2 sensor voltage ahead of cat. converter Bank 1}

_{O2 sensor voltage behind cat. converter Bank 1}

_{O2 sensor voltage ahead of cat. converter Bank 2}

_{O2 sensor voltage behind cat. converter Bank 2}

_{Should be very obvious if you sort by "name" in the list of Actual Values.}

_{See my post here -- the names are also shown in my graphs:}

_{http://www.renntech.org/forums/topic/43522-p2096-porsche-fault-code-16-oxygen-sensor-ageing-delay-bank-1/page-2#entry234549}

_{Bank 1 in fotostar's post above looks bad. Bank 2 looks good.}