M111 is the only official command doing it. The lcd menu also has a option for it.
If it is decoupling/defect you also see it in the lcd as target temperature (dec/def). These are the only reasons to enable dry run while printing, but that should be accompanied with a reason.
For testing you could disable decoupling test setting decoupling time to 0.
Also run M104 to see if you get a temp. error report in log.
