One problem related to service engine light on has been reported for the 2012 Infiniti QX56. The most recently reported issues are listed below.
Vehicle dropped speed on the highway and started flashing the service engine soon light. The speed drop was severe and placed me in a dangerous situation on the highway. It also had a whining noise at start when I left . Took it to the dealer, they informed me the timing chain needed to be replaced. The vehicle only had 83k in miles and was just 10k out of warranty. Dealer charged $4000 for the repair.