SCClockDr wrote:
If you plugged in hot the EMS May have seen power before the ground. Remember P means previous if you now have good power the ground is good.
While possible, this should be unlikely due to the design of the plugs and sockets. The ground prong is longer than the hots (and neutral) so it makes contact first--at least that's the theory.
The EMS is actually looking for a voltage difference between the ground and neutral, and complains if it's anything much greater than zero. The actual problem could be a poor neutral connection somewhere, or a poor bonding between ground and neutral at the main panel, in addition to a poor ground connection. It cannot detect whether the ground is a good earth ground or not, since it has no reference to earth potential.