I have a 2013 Ram Pro-Master 1500…whenever the vehicle is going up a long steep grade the ESC will come on and HILL HOLD ASSIST SERVICE will appear and at the same time the vehicle will go in LIMP MODE…the RPM will be around 3500-4000 when this happens…No one has the solution for this problem.
The problem might be with the YAW sensor in the van.
Hill hold should operate only while you are stationary. A scanner hooked to the van to observe the sensor readings while you are driving should uncover if it is a bad yaw sensor or other. Plus reading the error codes from the stability control computer.