Hiya,
E3 indicates the appliance isn't heating.
This can be the element, thermostat, wiring or pcb that causes the problem.
Unplug the appliance and take off the inspection panel below the door.
Look in at the heater terminals, there should be a thermostat close by.
If you are lucky, there will be a push button on it. If there is, push the button.
If not, you'll need to have a mutlimeter and the ability to use it to test the heater and the thermostat.
Check them for continuity. This is the most basic check.
If you have continuity through them then they are probably ok.
If open circuit, you'll need to replace them.
Have a look and see what you find.
Hope this helps
Let me know how it goes or if you need more help.
Thanks
Home Appliance Technician
Whitegoods engineer working for a multibranded national company in the UK.