Smoke & Check Engine Code #P0420

[xugg]

Hey guys, I ran into a problem after a weekend of driving 500 highway miles and I was wondering if anyone else has run into this problem. The alti's got 108k on it and I threw in some fuel system cleaner in a full tank of gas before I left town.

Towards the end of the trip, I noticed some smoke particles/residue coming out of the exhaust under heavy acceleration ( ie. passing a semi )

Computer threw the code P0420 Catalyst System Efficiency Below Threshold about 3-4 days after the trip.

From what I found @ OBD-II Trouble Code: P0420 Catalyst System Efficiency Below Threshold (Bank 1)

A code P0420 may mean that one or more of the following has happened:

* Leaded fuel was used where unleaded was called for
* An oxygen sensor is not reading (functioning) properly
* The engine coolant temperature sensor is not working properly
* Damaged exhaust manifold / catalytic converter / exhaust pipe
* Retarded spark timing

Im thinking its just the O2 sensor picking up on the extra carbon being burnt off from using the fuel system cleaner or its just needs to be replaced after 108k? What do you guys think?

[mityay]

I had that code before and it kept coming up for 3 times after being reset. I had precat and upper o2 sensors replaced and they seem deteriorating. Toasted precat might be dnagerous for your engine because the precat particles might get into engine and score the walls. There's a lot of discussions on that
Anyway, I replaced it - it wasn't cheap but sure worth it. My mpg improved significantly

[twizzle]

REPLACE IMMEDIATELY. I already went through an engine (65k) Noticed smoke one day, a day later, engine died and barely made it to the dealer. Common problem with these shitboxes.....faulty cat, clogs up, heat backs up into motor, kaboom. I was lucky i only had to pay for labor, but still......be careful.

[xugg]

How can I tell if the precat is burning up?

[sialtima]

I'm not a big believer in this engine blowing up stuff with a p0420 code. Reason being.....I got this code at 81k miles, changed o2's, plugs etc to be certain it was that since nissan wouldnt warranty it because I was 1000 miles past the warranty time...the bastards! Went for a price and $500 killed me.....so didnt bother changing it. I am now at 104k miles and the only thing I can see its causing is a foul exhaust smell and crappy milage. A nissan tech and various mechanics also laughed at stuff getting sucked back into engine, they claim that its a very small chance that will happen and as for it being clogged to the point of no exhaust passing is also slim. Im not saying it cant happen but to put the experience of members here and the amount of Altima drivers out there the percentage is very small. Anyway I got tired of crappy milage and smell so My job was able to get me a the header/precat for a cool $275 from nissan....still alot but better then $500. Have to say though this thing is one ugly ass thing for being brand new lol...looks like a 2 year old welded it, going to give it a painting before installing it I guess.

[DryHeat]

Stop using additives. If the O2 sensor has never been replaced, it's time, but the most of the gasoline we buy has some sort of additive to clean deposits. No need to purchase anymore that might cause the car to pollute more or possibly damage it. What fuel system cleaner did you use by the way?

[VQPower37]

sounds like the catalytic converter ... my car had a 0420 code too .. i tried the 02 sensors, and reprogramming the ecu, and after both of those failed ... i finally had to juss buy a new converter ... which fixed everything

[ducz24]

change your catalytic converter immediately! it will cause a major problem down the road like replacing your engine cause it sucked it all up...

also search, there has been alot of threads on this matter

[xugg]

Are the precats really necessary and

would I still pass emissions tests if I put on after market headers?

[tsr0003]

none of the a/ headers have cats - have to get one put on the header. depending your state and emissions may be able to get get through a test with this setup.. no guarantees though. some states don't test emissions - simply looking for engine lights - so if you are 2004< get a/m headers range from 150 and up. Want to be cautious get a a/m cat welded on prior to install. If you aren't doing yourself be prepared to pay a pretty penny for the labor - these cats are a PAIN to change out

[xugg]

I'll replace the O2 sensors first. If the problem persists the next option is headers.

I'll keep you guys posted, thanks for the feedback.

[eskalaid]

ive had my 02 2.5 for about 2 months and like 3 weeks after i had it i got that codetook it back 2 the service center 7 times they kept saying it was the gas cap now i just got my car back yesturday and i had 2 give it back the next day... they said they changed the catalytic converter...but since they did that it sounds worse then it did b4...dam dealership sell a ****ed up car