Cat converters causing check engine light

[B-A-W]

Hey guys,

Been here for a while but haven't posted yet.

I brought my M in to have the codes run when the light came on and it was found to be the "P0420 and P0430....catalytic system efficiency below threshold banks 1 & 2". So I know its the cats on both sides of the manifolds but the dealership is saying that the pre-cats (which are part of the manifold) were the cause of the code. They then told me this would run just shy of 3 grand as they would have to lift the engine and replace the entire manifolds.

It seems more likely to me that the real cats would be the cause of this light....not to mention they seem to be rattling a bit. Was wondering if anyone else experienced this code and what they did to fix it.

Thanks,

Ben

[ezb57e]

Welcome.
Assuming they checked for any exhaust leaks, they are correct.
The cats on the manifolds are the main cats, and the only ones that are monitored.
The post cats have no sensor behind them.
Pay up and move on.
Its a great car and worth it.

[B-A-W]

I was afraid that might be the case....but its better than getting it wrong first time around. Thanks for your feedback

[svard75]

The cats are one piece and are three way. We dont have pre-cats or post cats. Not that I've ever heard of that anyway. Replace the cats and the codes will clear. That dealer is fishing for more money than required. You can buy replacement cats on ebay or through our sponsor infinitipartsusa.com then have any exhaust shop install them.

[The00Dustin]

I wouldn't know, so don 't want to get into an argument, but I'm sure I've seen other posts here about "rear cat deletes" and about the "secondary cats" not having oxygen sensors behind them.

I've also seen a lot of posts hi-flow cats and about custom exhausts being cheap when you go to a good local exhaust shop. Maybe you could get hi-flow cats and a custom exhaust (if the second was even necessary) for the same or less than replacing the manifolds with stock. I don't know if there would be any benefits or tradeoffs, but it might be worth looking into.

[svard75]

Dustin check the infinitipartsusa.com website they have the exhaust broken down with names and part numbers :-)

I think what people are assuming rear cats are they are actually resonators not catalysts.

[ezb57e]

Dustin check the infinitipartsusa.com website they have the exhaust broken down with names and part numbers :-)

I think what people are assuming rear cats are they are actually resonators not catalysts.

The bulbous objects in the front exhaust tube behind the main cats ARE catalysts, not resonators, and are required equipment to pass a smog check in any state. The "resonators" are found further down the exhaust system.

You need 2 new cat/manifold assemblies.
I don't think your dealer is "fishing" for anything.
Their use of the term "pre-cat" is debatable but they are still correct in their diagnosis, assuming as I mentioned, there are no leaks.
Ambient air can enter through cracks or missing/damaged gaskets and upset the oxygen storage capacity of a cat, and set a DTC.

[flex128]

I would make sure it's not the O2 sensor on the cat before spending the money to replace a cat. Just saying I had the same code changed my O2 sensors and no more code. And the rattling could be just loose heat shields on the cats I tore mine off and fixed that problem.
If you can I would try the O2 sensor first since its easy to take off and put a new one on then clear your codes if they come back then spend the money on cats sensors are cheaper then cats and a quick fix if thats your issue.
As for the dealership I wouldn't trust everything they say.

[TDot]

....not to mention they seem to be rattling a bit.

Could you explain this rattling a bit more if that's possible?

And the rattling could be just loose heat shields on the cats I tore mine off and fixed that problem.

You mean on the outside, under the car right?

When I had my contentious issue with the dealer about clicking in my wheel and he lifted my car up, he said he heard rattling in both my catalytic converters and they needed to be replaced. No lights on in the car yet though. My engine doesn't sound "smooth" anymore, there is a slight rattling like a pebble is being kicked around. Does that mean the cats need to be replaced...I just don't trust the judgement of this dealer anymore. Thanks.

[svard75]

Dustin check the infinitipartsusa.com website they have the exhaust broken down with names and part numbers :-)

I think what people are assuming rear cats are they are actually resonators not catalysts.

The bulbous objects in the front exhaust tube behind the main cats ARE catalysts, not resonators, and are required equipment to pass a smog check in any state. The "resonators" are found further down the exhaust system.

You need 2 new cat/manifold assemblies.
I don't think your dealer is "fishing" for anything.
Their use of the term "pre-cat" is debatable but they are still correct in their diagnosis, assuming as I mentioned, there are no leaks.
Ambient air can enter through cracks or missing/damaged gaskets and upset the oxygen storage capacity of a cat, and set a DTC.

From a unit perspective it is a single unit. It also is not a part of the manifold so if the dealer says you need a new manifold and cat that is BS.

[ezb57e]

The main cat is not removable from the manifold.
Are you looking at the V8?

[svard75]

apologies I just noticed the OP is refering to the M45. I was making references to the VQ35DE M35.

Please disregard all my entries in this thread.

[Double E]

BAW,

I just went through this issue. Look up my thread on it.

As noted, use the IOS source for parts. You will be charged a core fee until you send the bad parts back to IOS. At your expense but you'll get about $400 back.
I narrowed the issue I had with mine either to an idiot that used a seafoam treatment in the intake allowing lots of unburned fuel into the cats and it cooked them ...or a crank/cam sensor going bad allowed unburned fuel in. Once I replaced the sensors, that code was gone but the knocking started with no codes.

Either way, it knocked loud enough to make me think I lost a main bearing. I used a stethescope and was convinced the bearing was at issue but I never suspected the cats, so I never put the scope on them... No codes, just poor running and it would not accelerate as quick as before.

As far as the cats and manifolds go, on these 45 engines, the cat for each bank is a single piece unit with the manifold. As you can imagine, removal is tough but the engine may only need to be raised or lowered a little to get to them...on mine it did not require engine removal (but I have a Y34.)

I got the cat/manifold assemblies and the main cat with gaskets for about $1K less than the dealer. I had my local dealer put them on b/c I wanted someone familiar with the car to do it, not learning as they went or breaking something else. I paid a LOT for labor but it was done right, once.

[B-A-W]

BAW,

I just went through this issue. Look up my thread on it.

As noted, use the IOS source for parts. You will be charged a core fee until you send the bad parts back to IOS. At your expense but you'll get about $400 back.
I narrowed the issue I had with mine either to an idiot that used a seafoam treatment in the intake allowing lots of unburned fuel into the cats and it cooked them ...or a crank/cam sensor going bad allowed unburned fuel in. Once I replaced the sensors, that code was gone but the knocking started with no codes.

Either way, it knocked loud enough to make me think I lost a main bearing. I used a stethescope and was convinced the bearing was at issue but I never suspected the cats, so I never put the scope on them... No codes, just poor running and it would not accelerate as quick as before.

As far as the cats and manifolds go, on these 45 engines, the cat for each bank is a single piece unit with the manifold. As you can imagine, removal is tough but the engine may only need to be raised or lowered a little to get to them...on mine it did not require engine removal (but I have a Y34.)

I got the cat/manifold assemblies and the main cat with gaskets for about $1K less than the dealer. I had my local dealer put them on b/c I wanted someone familiar with the car to do it, not learning as they went or breaking something else. I paid a LOT for labor but it was done right, once.

Thanks this helps, the dealership quoted $748 for each side. Our local Nissan branch is pretty reasonable for labor though, I'd probably go with them for something like this. And yeah its mostly labor in this case. I believe the radiator needs to be drained and removed and the engine lifted a few inches.

My biggest concern is there could be several reasons this is happening. About 5,000 miles ago I had the engine replaced and they used the manifold assemblies and exhaust system from the original engine (which burned oil and had carbon buildup issues). So the potential for a gasket leak when they reseated them or a legitimate need for cats is high. I suppose I could check for leaks when the car is on a lift?

[ezb57e]

Exhaust leaks should always be ruled out when evaluating catalytic convertor function, the dealer should have done that as part of the initial diagnosis.
I hope they checked the old cats before putting them on your new engine.
Cats can break up and allow the ceramic grid to enter the engine, and cause ring/cylinder wall damage.
Of course they don't work well either when this happens and can set P0420 and/or P0430 DTCs.
Alternatively, your old engine may have had some other cause of oil consumption, and the cats were damaged that way.

[bakili]

Hey guys, bumping up the P0430 issue. Long story short - couple of months ago I've burned and then replaced my engine with 10K miles less than the car (car 100K, engine 90K as of this moment). For couple of thousand miles I kept having P0430 come up with newly swapped engine. I've changed driver side 02 sensor (NGK 24404) - P0430 still came up. So I've swapped out my cats to Megan test pipes - and P0430 still came up! What's confusing is why P0420 didn't come up now. I don't have either cats and technically Megan defoulers should have prevented any Cat threshold error from coming up.

I've already had engine looked at by mechanic 2K miles ago and he indicated that there was no misfiring going on and I can attest that my engine does seem to run pretty smooth. Is there problem with an engine that I can't understand? God, I hope not!
Or is it because of mysterious pre-cats that are part of manifold? If that is the case, can I just ignore it then because I don't want to spend bunch of dough again and my engine will be fine with bad pre-cat?
Any shining light of mechanical wisdom is deeply appreciated!

update: Hold on, did I totally get the basics wrong? P0430 (bank 2) is driver side and P0420 (bank 1) is passenger side cats, right?

[bakili]

Small update
So apparently according to my mechanic seafom will take 10K-12K to get through the system. He told me that after I informed him that checking my oxygen sensors, driver's side oxygen sensor had lots of soot on it and passenger side didn't. He knows that I did an engine swap about 4K miles ago and ran 3 cans of seafoam right away.
This makes sense now. I have a theory that swapped engine had either injection or spark plug issue prior being put in my car on Bank 2, which after I ran so much seafoam shot my driver's side cat. That's why even with test pipes I kept getting P0430 consistently and not P0420. Speaking of which I just got P0420 which made me happy (I know that's weird ) that it's probably just insufficient Megan defouler design rather serious engine problem. Mind you engine is running smooth and no hesitation. Just added L shape defouler to Megan RTP which I hope will solve the issue of SES.