Here is my situation: I have a 2000 SE that I have owned for about 2 years now. It has an aftermarket y-pipe and is cali-spec. For the first year I had it there were no codes at all then I started gettting the p0420 code occasionally and it would go back off. Now it has been on for a few months and my state inspection is coming up. I had the codes pulled at Autozone the other day and it has a p0420 and p0430 which are both cat related codes.

I have done some research here on the forums and from what I can tell it is one of three things:

1. there is a TSB regarding the po420 code that involves an update to the firmware of the ecm. I have called the Nissan dealer and this will cost about $100 for them to plug it up to the consult and flash it. This may or may not fix the issue.

2. Cat is bad. I was thinking about replacing with a Random Technology cat which is about $200 plus installation. Car has almost 105K so the cat could be bad after this mileage.

3. Possible bad O2 sensor. The previous owner says the O2 sensor(s) were replaced at 60K but I don't know if all or which ones were replaced.

I need to find out what it is soon because of the inspection I will not pass with the ses light on and I don't really want to end up doing all 3 of these things if I can help it.

Also I should mention that I am getting normal gas mileage and there is no rotten egg smell or anything and the car runs great!

You guys have any ideas on this and which one I might try first?

Thanks in advance!

 

2001 GLE and have the same symptoms as you describe.

I am all stock and i only get the 0430.

I'm going to try using a spark plug non fouler sometime this week.

For your case you may want to use an o2 simulator.

 

yeah I have thought about the o2 simulator as well but I would rather go ahead and get it fixed right if I can

 

thats a good thought... but those pre cats are expensive.... if u're running stock... but in your case... you will need a simulator since the Y Pipe you have may not have the opening to put in the second o2 sensor... but again... i may be wrong.. i'll wait for the veterans to chime in

 

P0420 and P0430 are codes for your pre-cats, not the main cat, so I wouldn't bother getting a replacement for your main cat, since the codes don't indicate that you have a problem there.
Are both pre-cats still on the car? If not, then you'll get those codes (do a thread search - this is pretty common - O2 sims are the only fix I know of)
If the precats are there, then the FSM will tell you to:
Check for exhaust leaks anywhere upstream (toward the engine) of the main cat
Check for intake leaks
Check for proper O2 sensor operation
Check for leaking / improperly operating fuel injectors.

If I were you, I'd check for exhaust / intake leaks first, then check O2 sensors. I guess the leaky fuel injectors is possible, but I've never heard that was a problem on our cars.
I recently went through this with my car. My car has 135K on it, and at about 115K I started getting P0430 codes. After checking for leaks, I tried replacing the downstream O2 sensor first (FSM told me to), but still had the occasional code. At that point, I knew I was looking at a new pre-cat for $300 or I could try replacing the upstream O2 sensor for $60. I chose the cheaper option, and haven't had a code over the last 10K or so.

 

zoner... so basically u're saying you swapped out the o2 sensors on the radiator side bank of the motor and you're still running old o2 sensors on the firewall side bank?

why would you not want to keep all the o2 sensors of the same age?

 

I've been getting the same codes too and clearing them with my OBDII then they come back about a month later.

I added new bosch o2's when I put on my Y and new Bank 1 precat. I assumed the bung off of bank 1 downstream would fool the downstream bank 2 o2(firewall side).

One thing I did with the universal Bosch o2's - it comes with that splice piece - so you cut off the old o2 about 6" from the harness and used the splice piece to splice in the new o2. I'm wondering if that's whats causing the thing to trip as well.

 

How do you ?
Check for leaking / improperly operating fuel injectors.

 

Thats not true, p0420 can indicate a main cat problem.

 

1) 'Cause I'm cheap
2) If it ain't broke...

 

I can't say that's impossible. The FSM makes no mention of a possible main cat problem (just refers to '3-way catalyst (manifold)') with either of those codes, but it wouldn't the first time something was left out.

Also - sorry, missed 2 other possible causes in FSM: improper ignition timing, spark plug.

 

I have the 0420 on my 99 cali spec and it sets the light on and off by itself. It was on for the last 1000 miles and then randomly turned off one afternoon after work. It has me stumped as it could me numerous things....

 

Im getting p0420 on bank 1 sensor 1 which is downstream of the main cat (2000 fed spec)

 

Man, I knew the exhaust on the 2000 fed vs 2001 were different, but I didn't know they were that different. (Thought you still had O2 sensors right after each pre-cat, but I see you don't). Thanks for the correction.