Cause 

Pedestal washer is being operated without a full-size washer.

E7 will be displayed if a washer is not installed on the pedestal washer.

Solution

The pedestal washer will not operate as a standalone unit. It must be stacked under a full-size LG appliance.

The stacking safety switch will not operate properly if the unit is stacked under a non-LG appliance, or an Lg appliance manufactured before 2009.

Cause

Stacking Safety switch is not working properly.

Solution

Check stacked switch for continuity and insure LG brand washer is stacked on top of unit.

The Safety Switch is located at the left rear corner. The switch is closed when a washer is installed on the base.