Let me explain this more. The P420 code says that the cat isn't burning the excess air/fuel mix enough as if it had a straight pipe or was missing. My new SLP high flow cat I got with my headers does this at least once per month.

Now that cat can be clogged an giving to much back pressure or other problems that might cause hesitation but if it is burning the air/fuel that is going through it fine it won't throw a code as it shows things are all right.

 

Let me claify that, as I am now getting P0420 codes myself. A CLOGGED cat' will not throw a code, as far as I have experienced. I haven't figured out my problem yet. Is it the front oxygen sensor?

 

The P420 just says the burn isn't there which means there is either too much flow in the case of an aftermarket or that the cat itself is getting bad.

If you have an aftermarket cat I would just clear the code and not worry about it. Once I get into programming with my HP Tuner I'm just going to pull the code.

 

I just took my 02 SS to local dealer today with same problem, and it was the Cat

 

Thanks for bringing back a 4 year old thread!:p

 

Im having similar problems with my 06 LT... seems like a lack of power somewhere at certain times of driving. Ive been told it could be a bad cat or tranny fluids need to be flushed. Im very dissapointed with my self because i just had the monte in a exhaust shop and didnt bother to ask if they can look at it. Can you blame me though? After having a nice flowmaster installed im sure most of you would forget about all your problems and just dive away!! lol

Now im looking to have the cat replaced, however im not sure of what to get. Seeing as it must be replaced i might as well get something high performance/high flow cat. Anyone have any ideas of a good brand. Im mostly interested in something that can help give me a better tone then stock, not so concerned of how fast it will make me go . If anyone has an exact part number of their favorite cat that will fit in my 06 3.5 monte and give me a nice sound so i can run out and pick it right up that would be awesome!!!!

 

My 03 had the same issue, the way to verify is to pull the 02 sensor on the exhaust manifold (firewall side, Yes it is tight to get to) and take it for a ride with it out. It will wake right up (run properly) if the cat is clogged.

 

So this thing has a ton of problems. Amazingly it ran long enough to get me 300 miles back home, but the heat inside was incredible. I have 4 error codes.
P0036, P0102, P0141 and P0455. I know some can be tripping others. The question is what do I fix first? Car runs but has little power. Temp ran anwhere from 208 to 245 sitting in traffic. From what I have read I have the typical problesms, including the only guage working on the dash is blower pressure. Strangely, the cruise works fine, and the radio and A/C. Drives very good. I plan to restore this car, but need a starting point. Any suggestions?

 

Yes, start a new thread. The chances of getting useful responses at the tail of a bumped 13 year old thread are very low.

 

I realize that, but a car is a car. Same issues no matter how old they are. But if that is what it takes I can do that.