P0174 back "System Too Lean". OBD Fusion report attached. Trims look off yet MAF's look pretty close. Rough idle again. The fact that I swapped MAF's 2 days ago and it moved to bank 2 now would make you think that MAF's are the problem yet MAF A & B numbers are very close to each other on report.

It crossed my mind to to clear codes, swap MAF's again and relearn procedures and wait to see if it moves again to bank 1 as P0171 before I drop $400 on MAF's.

Any thoughts?

Thanks

 

Items that stand out:
• From the freeze frame: a long term fuel trim of 15% when the code was declared.
• From the Mode $06: In the misfire section, you have a higher than expected misfires. mostly on cylinder 5 and 6. (both banks)

Two things come to mind:
(1)
• Fuel pressure. Since the fuel pump is 10 years old, the fuel pressure should be checked to rule it out.

Here is the tool required and process to test fuel pressure:


(2) Datalog the following:
• Absolute throttle position
• O2 voltage (Bank 1, Sensor 2)
• O2 voltage (Bank 2, Sensor 2)
• O2 sensor lambda (Bank 1, Sensor 1)
• O2 sensor lambda (Bank 2, Sensor 1)
• Mass air flow sensor A
• Mass air flow sensor B

Drive the car for at least five minutes to get the AFR/O2 sensors up to operating temperature, then do your best to get a few wide open throttle runs from a stop and while moving.
From this we will be able to see what is going on with the fuel mixture at different engine operation conditions.

From a past research project, I have a few years of this exact data and maybe something will stand out.
Good luck!

 

CJ Motorsports have not had the tap in so waiting. In the meantime this gauge below looks ok to use once tap is available. CJ's mini gauge is not available till November.

• Replaced PCV's and hoses, Cel's P0171 and P0174 continue to come back. I run reports save and clear. These codes become "permanent" but eventually clear themselves after driving for a while, then come back.
• Checked exhaust for leaks using a vacuum cleaner on blowing mode, no exhaust leaks that I can tell. Could not spray soap on exhaust manifolds (shields present) but everywhere else downstream has no leaks.
• Fuel hose picture attached. That hose looks awfully new so I wonder if it was replaced before I purchased car and why.
• Is data logging below any different than the reports I've been providing?
• (2) Datalog the following:
• • Absolute throttle position
• • O2 voltage (Bank 1, Sensor 2)
  • O2 voltage (Bank 2, Sensor 2)
  • O2 sensor lambda (Bank 1, Sensor 1)
  • O2 sensor lambda (Bank 2, Sensor 1)
  • Mass air flow sensor A
  • Mass air flow sensor B
• 
  

 

Attached 3 reports today as much acceleration as I could.

• New OEM MAF's on the way (I want to start with a good baseline since these seems to be an often culprit).
• CJM fuel tap with fuel pressure gauge on the way.

 

Try reading through this thread https://www.myg37.com/forums/showthr...errerid=369648 its primarily about MAF sensor issues / air leaks - MAF sensor bank 1 and bank 2 codes.(not the codes you are seeing, but there may be a connection) Bottom line is someone suggested putting permatex on the the MAF sensor seals. I tried it and it seems to work so far, ~600 miles nearly a record distance without issues.

 

• A couple of reports with wide open throttle attached from 10-9-21 before fuel pressure test today.
• Disregard low tire pressure CEL CODE, temperatures dropped in this area same day, taken care of.
• New code came up same day of open throttle reports after a long drive at home idling, P0507, Trouble diagnosis (Idle speed control system RPM higher than normal, more than 200 rpm). Possible causes (Electric throttle control actuator, Intake air leak, PCV system).
• Fuel pressure checked satisfactory 10-11-21. 52 psi @ idle. 44 psi @ engine off after 30 min. Pictures attached.
• Re-installed engine cover which I had taken off about 6 months ago and clear All CEL CODES. Will drive car and see.
• Common denominator between previous codes P0171/P0174 and latest code P0507 are: Intake Air Leak and PCV system (I already replaced PCV hoses and valves).

• Anything you can tell from reports? Seems to me next stop would be to check for an intake/vacuum leak with a smoke machine. Your input is appreciated.
• Saw this video a while back where OP finds a leak on G37 at intake manifold collector insert (
  You Tube
  ). Is that the right way to check for an intake/vacuum leak with a smoke machine in G37?
• Don't have much experience with this but found this smoke machine to check it. (
  You Tube
  ). (
  Amazon
  Amazon
  )
• Other option would be to take it to a local mechanic.
• Thanks for feedback on Permatex fix at MAF sensor seal point. I was curious about this possibility especially given 3rd party MAF sensors so I measured MAF seal and mating surface at air box with a caliper a while back. Dimensions looked good to me even with with 3rd party MAF sensors. I doubt this is my problem but once I clear or confirm air leak elsewhere this could still be on the table. Thanks.

 

Since last posting used the above mentioned air smoke machine and it worked like a charm, no leaks detected. Have ridden the car and all cel codes clear but rides a bit rough. UPS lost sensors ordered. Once I can install I'll see if it makes a difference.

 

No Original new MAF sensors yet but 3 days ago heater connector busted and coolant leaked badly. Attached link below. New heater connector and clamps installed, refilled coolant and tested good. The heater connector had been slowly leaking over several months and I didn't know that's what is was. It finally busted 3 days ago on 11/21/21 and it makes me wonder if air was also getting in there (heater connector) and creating this post original codes back on 9/8/21, almost 3 months ago. The codes on this posting were more prone to show when outside air temperature was higher. OBD Fusion report after fix today attached at 33 MPH shows Fuel Trims ok and MAF ok, no misfirings.

SonicVQ- Is this possible?

https://www.myg37.com/forums/engine-...ml#post4303583

 

• P0171 back on 11/30.
• Installed New OEM MAF sensors on 12/3, resistors look fatter on 3rd party MAF. Performed all 3 relearn procedures. Car feels smoother when it warmed up with no small hesitations, even smoother shifting. Trims are within specs as well as MAF readings, no misfires.
• Don't believe this is done with until I drive for at least 1,000 miles or even thru warm weather when I noticed this codes were reoccurring.

Aside from new A/F sensor and Fuel injector below everything else has been checked or replaced.
• Intake air leaks • A/F sensor 1 • Fuel injector • Exhaust gas leaks • Incorrect fuel pressure • Lack of fuel • Mass air flow sensor • Incorrect PCV hose connection

 

Not that I can see...

 

From what you have described, I think you just might have it figured out... As you mentioned, time will tell.
I wish you the best of luck!

 

This thread is quite interesting props to camb003 for the excellent documentation.
I believe like Sonic that you might have reached the end but we may never know.

I developed a theory based about your issue being a MAF from:
Prior K/N
Voltages being a bit off a bit
Air temperatures

I aftermarket filters filter less, we all know this however in the G especially with how almost direct the cold air feed is we don't seem to take into consideration how much dirt the MAFs see. After modfying my air boxes I can say After 10k miles I saw some dirt that when cleaned it changed my readings.
With voltages technically as long as throttles voltages are the same MAF's should similar in voltage. You can swap MAFs around to confirm this.
With temperatures, they should be +/- 8-12 degrees from ambient temp at cruise and depending on your intake setup can see up to 130-150F (only one intake air temp being measured - bank 1) I noticed when my intakes were catching engine bay air my temps would increase at about 3-4 degrees per second vs 1 per second when they would be sealed and receiving air from the outside.

What's even more interesting is how different these MAF's are and your average folk would have gone for the amazon option only to come out like you have would have frustrated/stopped any progress for your average guy.
I've had great luck with cleaning some Hitachi OEM sensors so I always look out for voltage and pick the best of them since MANY Nissans shared the same sensors (Altima, Titan, dual TB Nissans)

I hope this is the end for your troubles and again I congratulate you in the documenting. May your reward be the fix finally!

 

This is a timely thread as today my 2010 G37xS sedan with 165K miles abruptly entered limp mode as I exited an interstate after a 40 minute drive. The ECU reports codes P006A, P010B, P0174 and the coolant level is down 1-2 quarts! Thanks for the insight; I'll start by inspecting that connector, though in my case steam was visible near the front...

 

The hose is fine and I can find no other leaks, so I'm thinking the low coolant was a red herring, especially after logging a significant MAF imbalance, checking the filters, and discovering a massacre:



I've never seen anything quite like that. Those are installed in 2018. It appears that they became clogged and buckled (tore!) under engine suction. I cleaned the TBs, installed https://www.fram.com/parts-search/CA10544, reset the codes, and everything looks good now! Sheesh.

 

^^^ Wow! I also have never seen anything like that...
Crazy!