Jason, currently the only 45 pint dehumidifier that Haier sell is Model # DE45EK or DE45EK-L or EK-T. If any of those matches the Model Number of yours, you can down load and print the Owners Manual from the link below. However, the model numbers I listed make no reference to Error Code E2. If your Model Number does not correspond to any of those numbers, your unit is probably no longer manufactured or available.
http://www.haieramerica.com/en/asset/product/4ba7175e54With that said, there are two things you can do. First, turn the Master ON/OFF Switch to OFF. Unplug the unit from the wall outlet and wait 12 - 15 minutes. Then, plug the unit back in and turn the Master On/Off Switch to ON. Did the Error Code clear itself. If so, set the controls as you normally would.
If that didn't solve the problem you can contact Haier Customer Service at 877-337-3639 and they will advise you what to do, to clear the error code.
Hope this helped you to solve the problem.