If there is the E1 fault code on the display and you have no idea what it stands for, do a few simple and useful steps. Some of them are pretty regular and pose no threat to your AC’s components. There is a good chance that the error will disappear.
Cleaning the air filter: turn off the AC and unplug it. Remove the front panel and then the filter. Rinse it out in soapy water, put it aside and wait until it dries completely. In some cases, filters become contaminated beyond repair and need to be replaced.
Check the buttons: not unlikely, one of them is stuck. Press them all one by one and free the stuck one, if any. Most likely, the fault code will be cleared.
Try resetting it: just like any electronic device (a chip, DSL modem, etc.), control panels in ACs get grow “tired” after lengthy use and need a reboot.