2011 M56x - P0174 and P0448

Forum for Infiniti M37, M56 M35h Hybrid and Q70 owners.
User avatar
Ilya
Moderator
Posts: 9800
Joined: Fri Apr 23, 2010 11:20 pm
Car: 2011 M56x but I spend a lot of time on my 2015 Kawasaki Vulcan S. Former owner of a 2007 M35x. Also take care of my wife's 2016 QX60.
Location: Charlotte, NC
Contact:

Post

2011 M56x. 140kmi. About 5 minutes into my trip, noticed that the car was idling at about 1.1KRPM which is odd. When I got home and started to get my OBDII setup, I noticed that heat coming out from the underside was crazy hot too.

After I scanned the codes, I reset them and immediately idle went down to around 625 (car was running the whole time).

Questions:
  • What's the most likely cause of a P0174? Is it my front (upper) O2 sensors? I did replace the back/lower sensors when I did the O2 sensor extenders to combat my P0420/P0430.
  • Is the EVAP code related or is that something else entirely that's brewing and just coincidence?
Thoughts?

https://www.engine-codes.com/p0174_infiniti.html
https://www.engine-codes.com/p0448_infiniti.html

Image


User avatar
VStar650CL
Technical Expert
Posts: 8296
Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Post

The P0448 is probably coincidental, it means the ECM tried to open the Evap Vent Valve (probably to purge while running) and didn't get any response from the pressure sensor. The culprit is usually a stuck valve or a full/flooded Evap Canister. It won't be electrical, that would give you a P0447.

Extreme heat under the car is a bad sign, it probably means unburned fuel hitting your Bank2 cat. That most likely means the ECM is misdiagnosing the lean condition and dumping too much fuel into the mix. If your M has the dual MAF's, the first thing I'd check is for debris in the one on Bank2. It's also possible your A/F (front O2) sensor is malfunctioning and causing a non-stoichiometric run condition.

User avatar
Ilya
Moderator
Posts: 9800
Joined: Fri Apr 23, 2010 11:20 pm
Car: 2011 M56x but I spend a lot of time on my 2015 Kawasaki Vulcan S. Former owner of a 2007 M35x. Also take care of my wife's 2016 QX60.
Location: Charlotte, NC
Contact:

Post

VStar650CL wrote:
Fri Aug 12, 2022 4:55 pm
The P0448 is probably coincidental, it means the ECM tried to open the Evap Vent Valve (probably to purge while running) and didn't get any response from the pressure sensor. The culprit is usually a stuck valve or a full/flooded Evap Canister. It won't be electrical, that would give you a P0447.

Extreme heat under the car is a bad sign, it probably means unburned fuel hitting your Bank2 cat. That most likely means the ECM is misdiagnosing the lean condition and dumping too much fuel into the mix. If your M has the dual MAF's, the first thing I'd check is for debris in the one on Bank2. It's also possible your A/F (front O2) sensor is malfunctioning and causing a non-stoichiometric run condition.
Thanks as always sir. I guess I'll have to monitor for a bit to see if this comes back. Car is due for brakes, brake fluid, oil, air filters, cabin filter and PCV all in around 1kmi (when I actually hit 140kmi, I'm a hair under).

If it does, I honestly wouldn't be surprised that the top O2 sensors (have no idea if they are upstream or downstream - those terms always confuse me lol) are out. Don't O2 sensors last like 110-120kmi on average? I changed my bottom ones 2 years ago at like 130kmi so wouldn't be surprised if my top ones are out. But last I remember, those are an absolute pain to get too (especially considering I don't have a lift anymore)...so that'll probably be like a $1k trip to the dealer I'm guessing.

User avatar
Ilya
Moderator
Posts: 9800
Joined: Fri Apr 23, 2010 11:20 pm
Car: 2011 M56x but I spend a lot of time on my 2015 Kawasaki Vulcan S. Former owner of a 2007 M35x. Also take care of my wife's 2016 QX60.
Location: Charlotte, NC
Contact:

Post

I'm guessing if I did want to pursue the O2 sensor angle I'd need two of these (PN# 22693-1MC0B)? https://www.infinitiwholesaledirect.com ... OC1nYXM%3D

Or rather, 2 of these (I love Bosch OE sensors - PN# 17012): https://www.ebay.com/itm/295139171534?f ... SwQ4xi2Gzf

EDIT: For the EVAP, it would be one or both of these?

Canister Assembly - Evaporation - Infiniti (14950-JK60E) - https://www.infinitiwholesaledirect.com ... wtdjgtZ2Fz
Sensor - Boost - Infiniti (22365-1TV1B) - https://www.infinitiwholesaledirect.com ... wtdjgtZ2Fz

User avatar
VStar650CL
Technical Expert
Posts: 8296
Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Post

Feed InfinitiPartsDeal your VIN and double-check the part numbers there. IPD is the same as NPD, their dbase and diagrams come straight from Nissan DPC. So if they say it fits your VIN, you can be pretty certain it does. Then you can xref to Bosch or anybody else you please. My customers actually haven't had much luck with Bosch O2's, but maybe that's just dumb bad luck. Vis the canister, if it's easy to drop then shake it and weigh it. It's more likely you have a stuck valve than a flooded canister, so if it isn't easy to drop, I'd try a valve first.

Upstream and downstream are a pretty simple concept, just think of the airflow through the engine as a river travelling from source (the airbox) to mouth (the tailpipes). So the upstream sensors are the ones the flow reaches first, ahead of the cats. The downstream sensors are further downriver, after the cats.

User avatar
Ilya
Moderator
Posts: 9800
Joined: Fri Apr 23, 2010 11:20 pm
Car: 2011 M56x but I spend a lot of time on my 2015 Kawasaki Vulcan S. Former owner of a 2007 M35x. Also take care of my wife's 2016 QX60.
Location: Charlotte, NC
Contact:

Post

Thanks for that analogy, it does make it easier to understand.

I've never had an issue with Bosch and I've been using them exclusively as OE replacements on my Maxima's and both of my M's. But I guess with anything mass produced, bound to run into some duds.

User avatar
Ilya
Moderator
Posts: 9800
Joined: Fri Apr 23, 2010 11:20 pm
Car: 2011 M56x but I spend a lot of time on my 2015 Kawasaki Vulcan S. Former owner of a 2007 M35x. Also take care of my wife's 2016 QX60.
Location: Charlotte, NC
Contact:

Post

So today I had P0171 also come up (as pending) which is System Too Lean (Bank 1) which is the other bank (https://www.engine-codes.com/p0171_infiniti.html). Both banks together would suggest that it's not sensors but maybe indeed an air leak. I did recently remove the intakes to do an AC Condenser install and put it all back as I have 100 times before...but maybe something isn't sitting right after it's been driven/jostled?

Will report back.

User avatar
Ilya
Moderator
Posts: 9800
Joined: Fri Apr 23, 2010 11:20 pm
Car: 2011 M56x but I spend a lot of time on my 2015 Kawasaki Vulcan S. Former owner of a 2007 M35x. Also take care of my wife's 2016 QX60.
Location: Charlotte, NC
Contact:

Post

Welp, I think I fixed the issue in 10 seconds.

Evidently, when checking my oil last time, I forgot to re-install the oil cap. Luckily, the oil level is fine (checked today) and oil wasn't spewing all over the engine bay (don't understand how it wasn't), but I reinstalled it, cleared my codes and did a drive and all OBDII drive tests were completed and no codes.

Oops.

User avatar
VStar650CL
Technical Expert
Posts: 8296
Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Post

We've all been there.

:lolling: :dblthumb:

EdBwoy
Moderator
Posts: 3507
Joined: Tue Dec 25, 2012 12:47 am
Location: Indiana, USA
Contact:

Post

Ilya wrote:
Mon Aug 15, 2022 6:58 pm
Welp, I think I fixed the issue in 10 seconds.

Evidently, when checking my oil last time, I forgot to re-install the oil cap...
Yup! That will do!
I'm glad you were able to patch up your "air leak" with relative ease, and at minimal cost.


Return to “Infiniti M37, M56, M35h Hybrid and Q70 Forum”