"PE" error message on LG Dishwasher...

Question

The error message of "PE" comes on the screen when I try to run a cycle. If I open and close the door and try it a couple of times the error message finally goes away and you can start the cycle.Occasionally the cycle would stop with the "PE" error again in the middle of the cycle and you would have to start all again.There is no troubleshooting guide for "PE", there is "IE" "OE" etc so not sure what "PE" stands for??What can I do so that the machine operates as it should without having to fluff around?