Press "Up," "Down," "Up" and "Down" again on the timer controls to enter the diagnostic testing mode. The LCD lights will flash and "88" will appear briefly on the screen. If you have the "E3" error, it will pop up and remain flashing on the LCD screen.
The "E3" error means there are issues with button entry. This could be a mismatched entry key, no connection at all, or just a general glitch.
Check the connections from the control board to the dryer. There are two connection points that are simple plug and play ports. Every model features different port locations so refer to your dryer manual for the connection location. See if they're properly inserted. Unplug the connection points and reinsert them back into the control board to reset the connection. If the connections are not the problem then more then likely the main board needs replacement.