F40 error code

F40 is a communication error between the motor control board and the main interface control board. The big problem is that you don’t know which control board is causing the issue and there is no way to test, so it’s a guessing game. You can definitely take the dryer apart and make sure the wire connections are secure–but if everything checks good, a guess will need to be made and one of the control boards replaced. The most likely case I find is that the front interface board is the one having problems so that is the one I’d replace first.