2010 G37, 145,xxx miles - no mods or aftermarket, stock

I’ve owned this car for 10 years and bought it when it had ~25k on it. Now having major problems that are consistent but intermittent. I had given up on it, but the new and used car market is so terrible I’m reevaluating and trying to see if it can be saved. Need this to be reliable and everything about it is great, it drives great, looks clean and is a fun car, but is totally unreliable due to this issue.

Problem:

• Car suddenly starts shaking and jerking, max rpms are 2,400; once parked at idle RPMs are elevated around 1,000 RPMs
• Learned that this is the Infiniti LIMP MODE
• This occurs randomly with no obvious correlating driving conditions (weather, temp, speed, rpms etc.)
• Trouble codes confirmed multiple times at shop and with own OBD Fusion
  • P006A (Manifold absolute pressure - mass air flow correlation)
  • P0101 (Mass air flow sensor bank 1 circuit range/ performance)

Problems that occurred previously and since:

• Feb 2022 - rodent damage to wiring harness bank 2 (drivers side); repaired at local shop
• March 2022 - hit front left corner in a minor accident but required body work on quarter panels, new left headlight and new front bumper
• May 2022 - FIRST occurrence LIMP MODE; towed to shop that previously fixed rodent damage, they did diags, couldn't isolate problem, reset ecu and sent me on my way
• June 2022 - LIMP MODE reoccurs // took to a new non-Infiniti shop, they tested for short and ground faults on the MAF sensor and harnesses, had them replace spark plugs, all fluids changed including differential, coolant, etc.
• Sep 2022 - LIMP MODE occurs, same codes, replaced BANK 1 MAF w/ 22680-7S00A (self changed)
• Oct 2022 - LIMP MODE reoccurs // took to Infiniti dealer, they cleaned throttle bodies, reset ECU
• Dec 2022 - LIMP MODE reoccurs // dealer completed PCM Update per TSB: https://infinitig37.com/TSB/ITB11-060.pdf
• Jan 2023 - LIMP MODE reoccurs // dealer replaced MAF on Bank 2 (not sure why), reset ECU, relearn procedure
• Mar 2023 - LIMP MODE reoccurs // dealer found an intake air leak on Bank 1, replaced the air intake hose (part that goes between the air box and the throttle body)
• Apr 2023 - LIMP MODE reoccurs // car has been parked and mostly unused
• LIMP MODE reoccurs again in May a few times while driving short trips to grocery store and back

So, from my limited knowledge of being an armchair mechanic, I’ve ruled out the MAF sensor, the air leak on the intake hose. Cleaned MAFs, new OEM air filters.
Should I turn my attention to ground faults, open faults on the wiring harness? I did use an OBDII sensor and thanks to @MotorvateDIY videos I have a report (attached).

Any guidance suggested - help me keep my G alive! Local to DFW if it makes a difference.

Limp mode video - https://photos.app.goo.gl/uhquMsRr3NBbdxnW7

 

My expereince with a persistant limp mode with associated Bank 1 MAF code ended up being the MAF connector. Installed an ebay connector/pigtail about a year ago and have not had a problem since.

 

I am tagging @BULL here as he has extensive experience with these engine wiring looms and he may have other ideas...

As you have had two incidents involving the driver-side of the car (rodent/ collision) and the intermittency of your issue, my bet would be the harness. When the repair shop initially repaired the rodent damage, did they cut/ splice the damaged wires or replace the damaged section of the loom from pin to pin? What method (butt splice or solder)? Same gauge wire? Is the loom properly insulated? Also, are the grounding points clean and secure? The engine grounds on these cars is mediocre at best despite the rest of the electrics being pretty robust. I know these are a lot of questions and you probably can not answer most of them, however, the old days of just "splicing in a wire" does not really work on these modern cars where critical voltage readings- even down to the millivolt (mV)- demand accuracy, or errors ensue.

Do you have a multimeter/ diagnostic skills or are you going to be paying a shop? If it were me, I would start by testing each of the affected circuits for continuity from the ECU harness connector to the termination point. A solid circuit should read zero ohms (ØΩ). Keep testing the line while lightly manipulating the loom to check for any breaks in the line. The reading should remain steady at zero (Ø). If the reading fluctuates, returns a high number reading, or reads "OL" (open line) then there a issue with that circuit.

Worst case scenario, and likely the easiest path forward, find a local pull-a-part junkyard, or eBay, and get a replacement engine harness. It will be cheaper to just replace the harness than to spend hundreds or thousands having a shop diagnose/ repair.

 

Update for posterity - I've been using Premium fuel since mid 2022 when I needed to rely on this car again and have had no problems since - knock on wood!