The HE error code appears when there is a problem with the heater relay or heating element itself. You are going to have to disassemble the dishwasher.
The relay is found on the dishwasher’s right side, and you need to remove the metal panel to get to it.
Although you can test the heating element without tilting the machine, it will be easier if you put it on its back. In any event, the bottom cover needs to be removed.
Dishwashers’ heating elements and heater relays tend to go faulty in homes where families use instant (tankless) water heaters.
They require minimum water flows, which puts additional workload on dishwashers’ heating elements and heater relays. This reduces the elements’ lives, because they overheat every time a dishwasher is used.