# 420 code



## supertony51 (Jan 13, 2011)

Okay so heres my story,

So right now ima solider deployed to iraq, about 2 months before my deployment My 2001 nissan frontier 2.4l gave me a check engine light. after bringing it to the dealership they said it displayed a p0420 code which is the bank 1 catalytic converter. This truck only has 76k miles on it and its the second converter ive had to go through (first one was a warranty repl and that was at 45k miles)

My truck also has been running a little rough, it idles fine (but you can DEFINATELY tell its running rich from the smell) but when you go to accelerate it sputters and hesitiates and will stall out on the road, ive also noticed that the problem is 5x worse after it rains or alot of humidity in the air. I know that a bad upstream O2 sensor can cause this as well. I want to get this fixed when i get home, but not drop a ton of money on unessesary parts so....heres my questions if anyone can help me out.

1. should i change the pre-catalytic converter or the rear catalytic converter? i know my truck has both, but im not sure which one i need to replace with the p0420 code....correct me if im wrong but there is 2 catalytic converters?

2. Should i change the upstream O2 sensor as well?


3. If its the rear cat, is that a easy bolt on cat, or a weld job?

Any input would help alot, ive used this deployment to pay off crdit card debt and save a little, im really hopeing i don't have to go back into debt fixing this truck, especially sincce it has such few miles on it for these kind of problems

thanks


----------



## azrocketman (Oct 5, 2005)

Actually, the first thing I would do is clean the Mass Air Flow (MAF) sensor located in the throttle body. There are spray on cleaners intended for this purpose at the auto parts stores or you can use electronic contact cleaner. Whatever you use, be careful contacting the MAF sensor because it is relatively delicate. I suspect this may relate to your rough running problem. Also, I'd do a tuneup (plugs, distributor cap, rotor, maybe wires) if you have the original parts installed. I'd stay with NGKs for the plugs.

My 2001 Frontier with almost 150K miles is also periodically indicating a P420 code. If I'm going to just replace parts I probably would replace the upstream O2 sensor first (after the above steps). A better approach would be to find someone with a more sophisticated OBDII scanner that can look at real time data to see the switching of the forward O2 sensor and engine trims. Nissan should be able to do this with their Consult II system but if your dealer is like mine I have no faith in them.

And, thanks for your service in our military.

Steve


----------



## supertony51 (Jan 13, 2011)

*thanks steve*

Thank you steve for the help. I work for the citizens, so thank you for the privledge to serve.

Yeah i will try that out when i get home (cleaning the MAF sensor). What about the 420 code, is that for the pre-catalytic converter or the actual converter futher down the line?

I was also thinking of the upstream O2 sensor since it is running really really rich, is there a way to clean that and make it serviceable, or should i just replace it?

My dad is coming out for the re-deployment so we are both going to work on it a bunch as "father son" time, and will also be doing a tune up (all the stuff you mentioned, and a oil change and filter change)

Is the catalytic converter a simple nut and bolt install, or weld, and does anyone know how good the aftermarket cats are (130$ as opposed to nissans 500$ one)

Thanks all for whatever help you can give


----------



## azrocketman (Oct 5, 2005)

There is no way to clean or service an O2 sensor that I am aware of. Remove and replace is the only cure.

I need to look under my truck to see how the converters are plumbed in the exhaust. You're asking the same questions I need to answer relative to my truck. You might want to look at this site "www.courtesyparts.com". They have some good graphics that show part numbers and connections. 

I'll reply when I know more.

Steve


----------



## azrocketman (Oct 5, 2005)

I looked under my truck this weekend. It looks like the rear converter pipes are bolted on at each end. Other than fighting with rusted/siezed fasteners it looks like a straightforward remove and replace.

Steve


----------

