There is no fluid to add. These units use electric power steering not hydraulic. The light being on shows that there is a problem with the EPS. First thing is to check and clean all the electrical connections on the EPS unit. After some time these connections get corroded and dirty. I use contact cleaner and a small brush to clean the connectors out as much as possible. Next reassemble them using a little di-electric grease. If this doesn't work then it will be time to start troubleshooting the EPS unit itself. Just a side note there are other sensors that tell the ECM that the motor is not running and to turn the EPS unit off after a certain amount of time. This could be another cause for the EPS failure.
Occasionally my light will come on when started and I will have no PS….I restart and it’s always worked…I will track down connections and see if that’s the issue as mentioned. Either that or it’s about to lay it down.
I have a 2016 midsize 570. Mine was doing the same things that you all are saying. My problem was the voltage regulater. Sometimes it was puting out too much voltage. Just something for you all to check on.