'00 I30 P0420 Code - does it ever end?

[Kompresshun]

So my wife was driving my car last night and the check engine light came on, I hooked it up to my code reader last night and got a P0420(Catalyst effec. below threshold Bank 1) code. My first thought is great what now, I just spent $975 less than a year ago replacing the pre-cat to fix the P0430 code. I've already searched on the code and found out the basic info on it, seems like it's most likely the cat but could also be the air tube or O2 sensor. My first question is which cat is it that's potentially bad? Secondly, i've been thinking about buying Y-pipe for it so I was wondering if it would take place of that cat?

I'm trying to avoid taking it to a shop again for a diagnosis, seeing as i've spent almost $2,000 on it in repairs in the past year and money is tight at the moment so any help or insight would be greatly appreciated

[MTZI30]

Hang in there man. The first year i had my I it was a night mare. Catalyst, (At least mine was covered by emission warranty) coils, suspension, pads/rotors all around, ac compressor, radiator, radiator fans, plus some other random stuff that I cant even remember. Its an older car so itll have a lot of problems things are just gonna go bad. Ya sounds like you need a new bank 1 cat. Pretty common with these cars.

[loystock]

The P0420 problem is most likely the Bank 1 Pre-Cat (below the engine) or the related O2 sensors. You may have SMOG Check issue with the y-pipe so check your state emission requirements.

I almost forgot, there is an Infinti Technical Bulletin that covers P0420. It may involve reprogramming of the ECU (due to mis-diagnosis) OR replacement of the Pre-Cat and front O2 sensor, depending on the part number of the ECM. Refer to the link below.

http://ww2.justanswer.com/uploads/badda ... 0-054b.pdf

You have a 10-year old car and parts will likely fail as time goes by. A lot of components are rated @ 100K miles - plugs, O2 sensors, etc. Even Federal Emission warranty is only for 8 years/80K miles. Suspension components are typically replaced @ 60-90K miles.

The Maxima/I30 have better than average reliability. So as long they are properly maintained, they should last beyond the current average lifespan of 12 years/128K miles.

So you have had Bank 2 Pre-Cat (P0430) replaced last year and this time you have P0420 (Bank 1 Pre-Cat). Bank 1 refers to Cylinders 1-3-5 (close to the firewall) while Bank 2 is for Cylinders 2-4-6 (front of the engine, towards radiator). Bank 2 Pre-Cat is visible from the front of the engine while with Bank 1 Pre-Cat, you have to safely jack up the car (pax side) as it is under the engine.

The 3-way Pre-Cat and Main Cat, aside from oxidizing/reducing harmful CO, HC and NOx into less harmful gases, also store oxygen. In the 00 I30, each Pre-Cat has a front (upstream) and rear (downstream) O2 sensors. There is no O2 sensor in the main cat. The ECM controls air-fuel mixture as a function of throttle position, mass air flow, front O2 sensors, etc. Normally. the O2 sensors 'see' air-fuel mixture switching from lean-ideal-rich and so on. Due to to O2 storage capability of the 'cat,' the rear O2 sensors switch slower than the front O2 sensors. But if the Pre-Cat is worn out (unable to store O2), then the rear O2 sensor switch rate approaches the front O2 sensor switch rate. At a certain threshold, the ECM flags a failing 'cat' (low efficiency) and generates the fault code, P0420 or P0430, etc.

From my experience with Nissan/Infiniti cars, 'cats' and O2 sensors go beyond 10 years The first time I replaced an O2 sensor is this year - Bank 2 Rear on a 99 I30 and Bank 2 Front on a 97 Q45. I expect to replace O2 sensors in the coming years but I hope the cat will last the lifetime of the car (knock on wood).

The 'cat' and O2 sensors can fail prematurely due to contamination (oil, silicon, phosphorous, etc), poor quality gas, engine misfire and/or continuous exposure to 'rich' air-fuel mixture. So make sure you don have intake/exhaust leak, your spark plugs are not over 100K miles and the fuel injectors are firing correctly.

[Kompresshun]

Thanks for the info, I forgot to look back in here but it's been a month and the SES light hasn't come back on. I'm just going to leave it be for now since it doesn't seem to be kicking the SES light on regularly, maybe it'll hold off for a bit at least. It's been a great car and I plan on driving it for a few more years before it's time to replace it, so another somewhat high repair bill will be worth being able to drive it a few more years.