[CdnFrontier]

I've had this code pop up alot in the last month or so. Scan Gauge says the first O2 sensor (pre cat) on Bank 2 is open. I changed the O2 sensor with an NTK replacement 2 weeks ago, after 1 day the light is back on again. Baffled, I took the truck to a reputable shop for a full diagnostic, they said the sensor I just put in was bad (I did handle it very carefully I know they are precious). Replaced with another NTK sensor yesterday and the SES light is back on again (same P2A03 code). The tech at the shop mentioned using only an OEM sensor (I believe the OEM is a Bosch). This seems kinda silly? Anyone else run into this problem?

 

[CdnFrontier]

I replaced the sensor with a new OEM sensor yesterday and the SES light is still coming on throwing the same code. Anyone have any ideas as to what else would cause this P2A03 code to keep popping up? It seems to happen more frequently when driving around town rather than on the hwy.

 

[colin123]

post from another thread about the same code

"I have 45k miles on my truck, the dealer has changed a bunch of O2 sensors while it was under warranty, then I changed all 4 within the past 6 months when it ran out of warranty. After changing all 4 O2 sensors, I knew it had to be something else. that's when I started emailing the Nissan USA representative. I've been in contact with this Nissan rep in the US, and he at one point mentioned that it could be a fault due to an exaust leak. I looked under the truck while it was running but I didn't notice anything leaking at all. It seemed like a long shot. Until I started my truck up after it was sitting over night, drove it up on some ramps, and I noticed a trail of water (condensation) running down one of the seams of the CAT flanges. The leak was so small that I missed it the first time looking, but the water was a dead giveaway on the leak! It was coming from the aft flang on the drivers side CAT. Could this have been the cause of my P2A03 code? I then ordered all four flange gaskets and had them replaced all at once. Since I've had them replaced, my gas milage has gone back to normal, and I haven't gotten the P2A03 code! I've been checking every week with my scan tool, and nothing comes up now! I think I've got the problem beat!

So far, it has been almost two months since replacing the exhaust gaskets, and the truck has been doing great. No codes, and normal gas milage. I'll mark this as a win!! "

http://www.clubfrontier.org/forums/f8/cel-light-code-p2a03-46250/

check for leaks

 

[CdnFrontier]

Thanks for the post colin123. I did come across that post when I first started getting this code, I actually spoke with the original poster. I did check for exhaust leaks at both cats on each side and didn't see anything. I am going to double check again over the next few days to make sure I haven't missed a potential leak.

 

[CdnFrontier]

Well had a mechanic friend do some more research today regarding my problem, as it turns out the ECU needs to be reflashed after installing an O2 sensor on these trucks. Seems kinda silly, I've replaced sensors in other vehicles without having to do this. Service rep at the Nissan dealer said it's very common. Crossing my fingers no more crappy SES light.

 

[colin123]

hmm thats good to know, and really weird. hope it works for ya

 

[CdnFrontier]

My guess is there has been some sort of issue regarding the O2 sensors on these vehicles. This is why perhaps the reflash is required. I'm going to ask the dealer more questions to see if this is a general Nissan thing or just specific to our trucks, perhaps this will help those with the same code in the future.

 

[CdnFrontier]

Back to the dealer again this morning. After doing a bunch of diagnostic work with the truck running it appears there was a small leak at one of the flanges in front of the cat. It seems to open up more once it gets warm, which is why I didn't detect it when I checked it since it was cold. I will update this thread on how the fix works.

 

[MEDEL514]

So whats the word??? What was the final fix???

 

[jhughes3281]

I just deleted that code with my OBDII reader.

 

[CdnFrontier]

So whats the word??? What was the final fix???

Changing the cat gaskets solved the problem. It seems that once the truck got real hot the gasket/flange would expand just enough to suck in some air and throw the code. This was discovered after the Nissan tech spent an hour on the phone with someone from Nissan tech. Code hasn't come back since.

 

[jhughes3281]

^ I will have to remember that when I get my headers and B pip done. Make sure it is air tight.

 

[aingrati8]

I have a 2006 Nissan Frontier SE 4.0 V6 with 192,000 miles. I have done general maintenance including changing the timing guides and having the entire timing chains replaced along with the water pump. I only use genuine parts as i'm the type that if i'm going to change it id feel better knowing that if it fails it wouldn't be because of cheap parts.

I recently was getting a p0420 and p0430 code along with a p2a00 and p2a03 I had both cats replaced although i purchased after market cats because the muffler shop and after reading there are no effects in using them. Them may not last as long but for what I paid I could replace them 4 times.

After changing the cats I was still getting a p0420 code along with a p2a03 and p2a00 so I started to research the cause of the codes and found spark plugs, intake leak, fuel injectors, exhaust leaks, timing.

I bought a fuel injector cleaning machine since the truck had high mileage and decided to do a very good cleaning of them while on the truck. I eventually ran 4 cans of cleaner 3 otc and 1 can of bg these cleaners are specific for only use in the machine not gas tank treatment. WOW what a huge difference in mpg gains I noticed a huge difference in the trucks performance and response, but I was still getting the p0420 and the p2a00 and p2a03 and each time I would clear the codes and start again. I took it as far as every time I did a reset of the code I would do the MAF relearn process and reset the fuel trim values to start fresh.

The I decided to change the spark plugs and at that time I would be removing the intake to make sure I dont have a leak at the intake gasket. When I removed the coils on the driver side (bank 2) and started removing the plugs there was oil in the spark plug tubes on cylinder 4 and 6 and when I got to the passenger side (bank 1) the same issue oil in the tubes on cylinder 3 and 5.

Now I need to do a valve cover gasket seal and change the spark plug tube seals. Heads up the seals on the valve cover CAN NOT be replaced you need to buy new valve covers. Even though you can buy the seals they cant be replaced. Well they can if you want to damage the valve covers. What happens is the valve cover splash guard inside the cover is molded into the cover and the seals are installed before that shield.

Now with new intake gasket and valve cover gasket, spark plug tube gaskets everything is sealed up and code p2a00 goes away. The only thought I have is maybe the spark plugs or sealing the gap between the spark plug tubes. I dont know the exact reason, but it went away.

Now i'm still getting the p0420 and the p2a03 and the one that always hits first was the p2a03 before the p0420.

Next I take the truck to the exhaust shop that did the cats and ask him to make sure everything is completely seal and no exhaust leaks. He found 2 gaskets had small leaks, but not very concerning since they are after the cats. He fixed them and still getting the same codes p0420 and p2a03.

I'm losing my patients but i'm determined to get this light off for good.
My next attempt is to try the MAF sensor its the original one and I just never really payed attention to it.

Ordered one and installed it and that dreadful p2a03 code is gone. That code drove me insane to narrow down, but its gone and hasn't come back.

I was still getting p0420 so i've checked almost everything and having new cats i just can see them being the issue. So next i'm thing timing i purchased Nissan data scan 2 and was able to change the timing advance +2 degrees and the code hasn't been back its going to take more time driving it, but so far i've drove 200 miles and normally it would pop up after just 20 miles.

The advance timing of +2 deg has made the truck feel much better and also i've noticed an increase in the mileage. From what i have found the Nissan specs show timing advance at 15 when at idle + or - 2 deg it will not hurt the truck as its something that Nissan uses to put it into spec. I also read that no change in octane you can still use 87.

Also with Nissan Data Scan 2 you can change the idle. If you get that low idle at about 612-625 rpm and a slight shutter at idle then you can bump it up in increments of 12.5 rpm in the tool. I ended up raising it by 25 rpm

I bought the software and the cable they recommend on there website. Cable only cost about 16 bucks on amazon.

Things I did for each code:

p0420 and p0430 changed cats
was still getting p0420 advanced the timing +2 deg

P2a00 changed spark plugs (make sure theirs no oil in the tubes) The valve covers are vacuumed and could be the cause of a vacuum leak.

p2a03 changed the MAF sensor