2009 FX 50S Transmission Into Limp Mode

[gmgagne]

My 2009 FX50S (owned since 2010) with now 145K has experienced occasional episodes of dropping into limp mode about once a year starting 3 years ago. Stopped car. Turned off and restarted--drives perfectly until about a year later. Recently it went out again in early November (3rd episode) luckily when near dealership, pulled in and had codes pulled (courtesy), which showed P0729, Gear 6 Incorrect Ratio, with 11 possible causes (see attachment). It was end of day and no time to dig deeper. Car restarted and drove till 2 days ago, when it reoccurred. Time to dig deeper. Before I take her in for a deeper look, any experience out there about what can be causing? Led to believe there is an occasional known problem with a "module" (which can be replaced without dropping the tranny) through which these causes are linked into the code reading circuit. Any insight out there?

 

[planckscale]

Last 3 month, I had exactly the same symptom. Turned off and restarted after 2 minutes and the car would drive normal again.
At the beginning it was less frequent; about once a week, then it became 3 times a week! I scanned it with my Maxidas tool and got P0550 code - Power Steering Pressure Sensor Circuit Malfunction.
I replaced the Power Steering Pressure Sensor with a used one from a 2006 Nissan Murano. Never had such issue again.

 

[gmgagne]

UPDATE:
Just had diagnosis of worn tranny part in 6th gear, identical to what my technician found in an exact car (2009 FX50) two months ago at 139K (mine is 149K). That car had experienced same symptoms prior to diagnosis and resolution by installing a used transmission from a Florida salvage yard he has faith in. Technician has located a used tranny from the same yard with 59K for $2K shipped, with 12-month warranty for parts and labor. Total cost will be $3,500 installed--much better than estimated rebuild or (outlandish) new tranny. Infiniti transition to the 7-speed in 2009 was not their finest hour.

 

[onthemove]

59k miles on the transmission they say? I'd ask for proof.
You were quoted well over $3,500 for a rebuild? Look for another shop.