Ilya wrote: ↑

Sat Mar 12, 2022 12:44 pm

I believe the M56 cat is part of the manifold, at least that has been this community's impression...resulting in the motor needing to be pulled to swap them. Not sure if that is factual or not but that's been the thinking of this sub-forum for the past half-decade or so.

Ok good. I found the part # for the drivers side and am looking up the passenger side so I know what it would cost if I need to get it done.

Ilya wrote: ↑

Sat Mar 12, 2022 12:44 pm

I believe the M56 cat is part of the manifold, at least that has been this community's impression...resulting in the motor needing to be pulled to swap them. Not sure if that is factual or not but that's been the thinking of this sub-forum for the past half-decade or so.

Yep, on an initial look at the parts drawings it appeared almost like a Z setup, but I can see in the FSM that it's more like the gen1 Armada. Gotta be a PITA in an M-sized engine box, glad my old bones will never need to pull one. If they ever try to make me, I'll quit.

Big_Tone wrote: ↑

Sat Mar 12, 2022 1:27 pm

Ilya wrote: ↑

Sat Mar 12, 2022 12:44 pm

I believe the M56 cat is part of the manifold, at least that has been this community's impression...resulting in the motor needing to be pulled to swap them. Not sure if that is factual or not but that's been the thinking of this sub-forum for the past half-decade or so.

Ok good. I found the part # for the drivers side and am looking up the passenger side so I know what it would cost if I need to get it done.

The M45/56 primary cats are welded to the manifolds. They have to be changed as one unit. You can find them online cheaper than going to the dealership. There is a $190 core charge per cat. If you supply the cat(s) to the dealer or your mechanic for installation you will need to ship the old one(s) back to get the core charge back. Someone did this and posted it on an older thread. If you just take the car to the dealer they will charge you at least $2200 - $2400 per cat mainly because of the labor plus they mark up the price of the parts. Modern Infiniti in Winston-Salem wanted $4400 to replace both of mine. Since my car was running fine with no loss of mileage or performance I went with the O2 spacer on the driver's side. CEL went away and passed Forsyth County emissions no problem. Passenger side never gave me any issues but I was going to have it done anyway since the car would be on the lift. I would also replace the manifold gaskets if you decide to go this route.

V8 secondary cats are welded to the Y-pipe and as such, are not monitored so they have no bearing on emissions testing. For comparison, the M35/37 primary and secondary cats are welded together as one unit, and that unit bolts to the manifold. Changing V6 cats is a whole lot easier plus there are several aftermarket options such as hi flow and test pipes.

armybrat wrote: ↑

Mon Mar 14, 2022 10:14 am

Passenger side never gave me any issues but I was going to have it done anyway since the car would be on the lift. I would also replace the manifold gaskets if you decide to go this route.

+1. Those style cats are hard enough on a Titan/Armada, and that's a much bigger engine box. Since the engine on the M evidently needs to drop, replace everything that might be a future problem. Manifold studs too, if the old ones look crappy.

Yeah, it's a mess and a brutal design which is why many of us don't go that route unfortunately. I'd much prefer to do it right, but not when doing it right is at the $3.5k+ (good discount lol) price point.

I'm hoping I can keep my car 2-3 more years until the new QX60's start coming back from lease so I can trade in my car and my wife's '16 QX60 for a '22. The M56 is kind of a unicorn at this point (low production numbers, hard to find) but I don't know if I can justify having a garage queen now that we only use one car at a time most of the time (both work from home).

Hello! How's everybody ? I think you will think that this is not my place to post, because I am not so mechanically knowledgeable, but I dare to write.
I have a 2014 infiniti q70 v8, just 60 thousand kilometers.
Last week the oxygen sensors were replaced. When I received the car and used it for about 50 kilometers, the check engine came on, the dealer tells me that it is the catalytic converters and I have the code p0430.
My first question is... Driving the car with this code, would it only affect me for the annual inspection? Does the car still work the same without any problem?
From what I read, the greatest interest here in the post was to pass the inspection. Thanks in advance

It's very unusual for a cat to fail at that kind of mileage, so if it really is bad, I'd be asking why. But I doubt it's bad. Popping that code right after a sensor replacement is extremely suspicious. Was it the front O2's (A/F Sensors) that were replaced, or the rears? If it was the rears, I almost guarantee you either 1) one of the sensors is defective (or aftermarket and not working right), or 2) the repair caused a small exhaust leak that's sucking oxygen into the flow and fooling the sensor. I.e., one way or another, it was a bad repair. If it was the fronts, there's a good chance the bad old sensors caused carbon buildup in the engine that needs to be cleaned out, and a Cataclean treatment is probably in order because of it.

I know this is the cat forum, but have any of you guys had issues with the battery on your M56?? I’m replacing the battery about every year and sometimes battery dies if not driven often (like 3 days)

Glml216 wrote: ↑

Sun Nov 13, 2022 3:35 pm

I know this is the cat forum, but have any of you guys had issues with the battery on your M56?? I’m replacing the battery about every year and sometimes battery dies if not driven often (like 3 days)

Search this sub-forum for the ECM controlled alternator thread. Should have done that before but with 3 posts I'll give you a break .

Thanks man, I appreciate the break haha.

Hello all. I don’t own an M56 but bought an M37 with 73k miles recently which now has the P0430 code. But the car runs fine with 28 MPG and with no noticeable loss of power. I noticed the coolant reservoir was almost empty and the heater is not blowing really not air at 90F setting. This is another thing to fix sadly after only having the M for 2 weeks .

What would be the first approach to fix the P0430 code? I bought a bottle of Cataclean to try first - is it a good idea to do so? Would the O2 spacer work on M37’s as well?

Cataclean will definitely help if you have carbon issues, which a lot of M's do. Spacers will work on any engine, but check the cat temperatures periodically if you use them. The spacers are disabling your early warning system, and a meltdown on a Miller-cycle Nissan engine can be catastrophic for the whole engine. If the cat is working at all, the outlet temp will be hotter than the inlet. When the inlet is equal or hotter the cat is dead-dead and in danger of meltdown, so it's time to bite the bullet and replace it.

Howdy! I’m now getting the P0420 and every once in a while I’m getting the car running super rich with lots of exhaust fumes. I’m not sure if it’s blocked or what. I’ve used sea foam and Cataclean, and thought it fixed it for a bit, but now it’s becoming a real problem. At this point, I’m leaning towards replacing them all.

I’m at 150k 2012 M56s. Any suggestions would be welcome. Thanks fellas, merry Christmas!

I would definitely consider replacing if you have the funds for it. I'm getting to the point where even though I have a spacer to full the OBDII, I still want to get it done eventually so all is well.

I hear yuh. Can anyone confirm or deny if these fit the 2012 M56?

https://www.ebay.com/itm/276230430703?m ... media=COPY

splitnails wrote: ↑

Mon Dec 25, 2023 10:00 pm

I hear yuh. Can anyone confirm or deny if these fit the 2012 M56?

https://www.ebay.com/itm/276230430703?m ... media=COPY

That's VERY cheap. Likely extremely low quality. I'd avoid honestly. For a job like this where you have to do so much work (or have someone do it), I'd personally go OEM...at least that's my plan.

Ilya wrote: ↑

Tue Dec 26, 2023 7:23 am

splitnails wrote: ↑

Mon Dec 25, 2023 10:00 pm

I hear yuh. Can anyone confirm or deny if these fit the 2012 M56?

https://www.ebay.com/itm/276230430703?m ... media=COPY

That's VERY cheap. Likely extremely low quality. I'd avoid honestly. For a job like this where you have to do so much work (or have someone do it), I'd personally go OEM...at least that's my plan.

Yea I hear you. I think the issue I’m running into is, it’s gunna cost about what this car is worth…

splitnails wrote: ↑

Mon Dec 25, 2023 10:00 pm

I hear yuh. Can anyone confirm or deny if these fit the 2012 M56?

https://www.ebay.com/itm/276230430703?m ... media=COPY

At least according to Ebay. Q70 5.6 framework must have a little more room vs the M56 even it's the same engine.

I just started getting both P0420 and P0430 at the same time. I read that it may be the thermostat, so I tried to check and see what the temp was reading. The only thing I saw that referenced temp was this:



Is this what I should be looking at? If so, looks a little off, no?