This thread is very interesting as I my 2013 recently had a P0018 code pop up shortly after doing a service. At 130K, I did the oil change, spark plugs, PCVs, and air filters. Truck drove fine with no issues but after a few days and 100 miles later, the check engine light and restricted performance message came on. Even with the message on, the idle was smooth and there did not seem to be a loss of power. The engine sounded normal so I cleared the code and tried to see if it would come back. The truck is just under 131,000 now and I still haven’t been able to replicate the code. I’m a bit puzzled by it but plan to do the chains in the next few weeks for peace of mind, sourcing all the parts and tools now.