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Discussion Starter · #1 ·
So for the last month or so I've been dealing with several persistent codes that have really drove me bananas and if you own the following, keep reading and hopefully this will help someone in the same situation:

2002-2006 Nissan Altima 3.5L
2002-2008 Nissan Maxima 3.5L
2004+ Nissan Quest
2003+ Nissan Murano

So as the topic states, I'm an owner of a 2005 Nissan Altima 3.5SE V6 and for almost the last year I've been dealing with the dreaded codes P1273 and P0430 for those of you that don't know,

P0430- Catalyst Efficiency below threshold Bank 2

P1273- Air Fuel Ratio Sensor B1S1 lean shift monitor

About P0430 & P1273: Near the end of June 2015 I've had my main cat converter go on me due to bad ignition coils and three days later had it replaced along with 6 ignition coils, though my problems were over, but then these two codes popped up together all the time which later I've noticed they would pop up when I'm doing 55+mph on the highway and for those I've inspected for any air leaks, found nothing, changed downstream O2 sensor on bank 2, and A/F ratio sensor on bank 1, no different outcomes for both. To make this part of the story short, months later I bought a non fouler spark plug and drilled a 1/2 diameter and attached it to the O2 sensor for bank 2. No more P0430 after that, only problem was still P1273, once again replaced A/F sensor on Bank 1, did the self-clearing procedure, within 3 miles, it's back as a pending and another 2 its stored. So don't ask how but a few days later I found a bulletin (NTB05-095) took my car to Meineke to have my exhaust system inspected to find the precat on Bank 1 was no good (exhaust leak), they wanted to charge me around $1200 for part and labor, next day I went to a local auto parts store and got the precat for $280 and got it put in for $200. No more P1273 after that.

Now for the fun part:


Came up often a little before and after getting rid of the previous two codes. Changed fuel pressure damper, inspected for intake and exhaust leaks, changed air filter, PCV valve EGR valve, MAF sensor and intake manifold gasket, even gotten a fuel injector service done. Almost anything I've done didn't make a difference. Even switched back to the old MAF sensor, still didn't work. Now to the cause of the P0171, P0174 and occasionally P0300, the symptom that I've experience: the car would idle fine for 15 seconds, drop RPM for a second or two and idle fine again and it goes on. But never shut off, so again, I inspect for leaks and found nothing. Then I've done a PCV valve test, where I would take out the valve block the inlet with my finger and it'd idle fine again, but put in back in the engine and it'd run crappy again. Changed PCV valve and it made no difference. But my car had the symptoms of a bad PCV valve. Later I looked online where people experience the same things after buying their valves from places like AutoZone and Advance Auto Parts, so I go to the Nissan dealer to buy the PCV valve and compared both, the PCV valve from Nissan rattled louder than the one I've bought from Advanced which hasn't been in the engine for not even a month yet, had the OEM put in. No more funny idling, no more SES light and I've recently passed Star inspection.

Moral to the story: always buy a OEM PCV valve otherwise you can end up spending hundreds of dollars on parts and services you didn't need like I did. Hope this helps.

Admin and Sup Mod keeping the peace
7,596 Posts
Good write-up for those that don't believe in replacing with OEM. There's an old saying that goes like: "Pay me now or pay me much more later".
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