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I have a 2007 Fronty Nismo (4L) with 240 km. I've had her for about 10 months and love er to death. I changed the spark plugs in the spring. I was fearful they were original, but they were not. Had a coil-pack go this summer.

She has a 2 in lift with Wrangler A/T tires. I've not gotten great gas mileage since I've had her. I thought the plugs may improve that but they didn't. I get about 14 l/100km (16-17 mpg). I've attributed it to the tires and lift.

Over the last few months I've been getting a P0430 code. At first I could reset and it would come back after a week or two. Now it comes on within an hour of reset. I've scoured the forums and read everything from gas cap to new cats. I am suspecting its the cat but I don't want to replace that if its something like the o2 sensor.

So here is my question for you guys, can a P0430 code possibly point to the upstream O2 sensor? I read another post tonight that said that the O2 has its own code. I'd like to not replace both if not needed.

One last thing...over the last few weeks I've noticed a stronger exhaust smell. Tonight I pulled the truck into the garage (it had been sitting cold in the driveway). The wind was blowing into the garage so it blew the exhuast fumes in. It was pretty strong. Almost like a fuel/gasoline smell? My initial thought was if that left O2 sensor is bad its sending too rich of a fuel mixture through. But after reading the O2 has its own code, that made me think it really is the cat.

Lastly, if it is the cat, are there any opinions on the Walker 16468? There is one left on Amazon for $201 (Canadian) which seems like a good deal. If I should start with the O2, then should I get the tool? (the tall socket type or the short box head type?)


Ok, fire away!
 

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The front are "technically" air/fuel ratio sensors and not oxygen sensors. They look similar, but the air/fuel ratio sensors work a little differently and are a lot more expensive, unfortunately. When they fail, they "usually" trigger a trouble code (note the "quotation marks" on "usually"). They also work in a very narrow range, so they can be very hard to test even if you do have an expensive scan tool. Upstream catalytic converters due fail quite a bit on the 05-and-later Frontiers and Xterras with the V6 and the R51 Patfinders with the V6. More often than not, if you have only a catalyst efficiency code and no other codes are set...and assuming you confirmed that there are no leaks in the exhaust system...it's usually the converter, itself. That said, if you are smelling fuel in your exhaust, it might be worth checking into a little further before dropping a couple hundred bucks on a converter. I would start pulling the oil dipstick and checking for a gas odor and/or an overfill condition. If there is, replace the oil and filter and so a compression test, fuel pressure test and fuel pressure leakdown test. Leaking injector(s) or excessive fuel pressure, albeit not common on the VQ40DE, can cause a rich condition and also ruin a catalytic converter. I've already read about a few VQ40DE engines that have had an upstream converter come apart and cause scoring of the cylinder walls and low compression, similar to the early QR25DE engines in the first years of the L31 Altimas. As far as aftermarket converters, Walker is probably one of the best out there. I have one on my '06 Pathy and haven't had any problems so far. If I was going to replace the front converter, I would replace the front air/fuel sensor regardless.
As far as O2 sensor removal, once you get the plastic wheel well liner out of the way, it's really not to bad as far as getting the sensor out of the exhaust. The hard part is getting to the latch-style connector and getting it apart and re-connected. I use a short-style sensor wrench on these.
 

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Northern.Nismo, am curious if your exhaust system is OEM or aftermarket?

Good luck w/ your troubleshooting/repair.
 

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The front are "technically" air/fuel ratio sensors and not oxygen sensors. They look similar, but the air/fuel ratio sensors work a little differently and are a lot more expensive, unfortunately. When they fail, they "usually" trigger a trouble code (note the "quotation marks" on "usually"). They also work in a very narrow range, so they can be very hard to test even if you do have an expensive scan tool. Upstream catalytic converters due fail quite a bit on the 05-and-later Frontiers and Xterras with the V6 and the R51 Patfinders with the V6. More often than not, if you have only a catalyst efficiency code and no other codes are set...and assuming you confirmed that there are no leaks in the exhaust system...it's usually the converter, itself. That said, if you are smelling fuel in your exhaust, it might be worth checking into a little further before dropping a couple hundred bucks on a converter. I would start pulling the oil dipstick and checking for a gas odor and/or an overfill condition. If there is, replace the oil and filter and so a compression test, fuel pressure test and fuel pressure leakdown test. Leaking injector(s) or excessive fuel pressure, albeit not common on the VQ40DE, can cause a rich condition and also ruin a catalytic converter. I've already read about a few VQ40DE engines that have had an upstream converter come apart and cause scoring of the cylinder walls and low compression, similar to the early QR25DE engines in the first years of the L31 Altimas. As far as aftermarket converters, Walker is probably one of the best out there. I have one on my '06 Pathy and haven't had any problems so far. If I was going to replace the front converter, I would replace the front air/fuel sensor regardless.
As far as O2 sensor removal, once you get the plastic wheel well liner out of the way, it's really not to bad as far as getting the sensor out of the exhaust. The hard part is getting to the latch-style connector and getting it apart and re-connected. I use a short-style sensor wrench on these.
SMJ999SMJ,
I checked the oil. It was changed (with new filter) about 3000 km ago (summer). No signs of high oil level and no gas smell in oil. So I'm guessing I don't need to do all the pressure/leak down tests? I did narrow down the gas exhaust smell to only when the truck is first started cold. After a drive and warm-up, it doesn't smell nearly as strong (maybe no smell at all). What would that indicate to us?

Regarding exhaust leaks, how exactly would I know of that? It passed our strict Canadian emissions test back in Feb and the test facility was an oil change place with a bottom bay. I asked if they saw any leaks and the tech in the pit said you can generally hear any leaks and he didn't hear anything.

I also looked closely at the cats and exhaust system last night. The flanges are very rusted including the bolts. I'm guessing I will need to cut the bolts off. The end of the cat that connects to the manifold looks really hard to get to. I'm beginning to wonder if its worth it to me to have the local shop I trust do the work. It doesn't look like a very fun job without a lift. Or does it just look harder than it really is? Has anyone here done theirs on a 2nd gen Frontier before?
 

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Her are the causes the FSM lists. I'll read through the replies and post more shortly
 

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Troubleshooting procedure from FSM
Thanks Wet Dog. I appreciate these, but somehow in the upload they got shrunk too small to read. The resolution is too low to even zoom in. Can you repost full res or just reference the chapter and page number? I have a local copy of the Service Manual on my computer.
 

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Wetdog, I found the pages at EC-983. That's a lot of work to test. It seems to me it may be the cat. Any tips on detecting an exhaust or manifold leak?
 

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Well, it makes sense that it would be rich at cold start-up, as it should be. All you need to do to check for exhaust system leaks is have someone with a wet rag block of the end of the tailpipe with the engine running, causing back pressure. If there are any leaks, you'll be able to see and hear them.
Rust is always a pain when working with exhaust, however, Nissan exhaust bolts are usually pretty strong and sometimes an impact gun and a little heating with a torch will get them out. The real pain is that the heat shield covers the front bolts of the upstream converter and if you try to remove the shield, the bolts almost always break. So, most mechanics will trim-off the end of the heat shield that covers the bolts for access. You will need to remove the mid-pipe/downstream converter first, which is bolted to the back of the upstream converter. Remove the front wheel and plastic wheel well liner to access the front bolts/nut of the upstream converter. You will want to order some new plastic clips for the plastic liner as you almost always end up breaking a couple trying to remove them. You'll also need some new pipe gaskets, as well. Once you get the upstream converter unbolted, it can be removed from the bottom of the vehicle. Of course, don't forget to unplug the air/fuel ratio and oxygen sensors, first.
 
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