Three problems related to check engine light on have been reported for the 2012 Infiniti QX56. The most recently reported issues are listed below.
I had my catalytic converter replaced back in December 2016 . There was a recall for catalytic converter so I had it replaced. Now the check engine light is back on so I got it checked out and was told that I needed to replace the catalytic converter again. 35k miles later.
Was driving home, a/c was on, all lights was on, all of a suddenly lost of power to the engine and while going up hill, so I floor it so the vehicle so I can get past over the hill then I started to smell something through the vents like it was on fire coming from the engine bay so I pulled over and turned off the engine pop the hood but didn't see no fire, then when I tried to start the vehicle back up it wouldn't so I waited for few minutes and tried again, the vehicle started back up so I went on driving again but it didn't show any thing on the dash no check engine light at all. It done it again lose of power to the engine and I started smelling something burning like metal coming from the vents again lucky I was close to home when it done it again, I shut the vehicle off and put the scanner on it, it throw out 3 codes but it never showed up on the dash saying check engine light at all. For the 3 codes one was for fuel pump other was for 02 sensor and the other was ecm I believe, wish I wrote them all down.
At 82,000 miles the check engine light came on indicating both catalytic converters were bad. They are warrantied to 80k miles and of course manufacturer would not help. This needs a recall, google Qx56 catalytic converter and see how many people have had this issue.