My LG LDS5040ST dishwasher has been failing to clean on the top rack. I determined that the upper spray arms were not working. I have determined that the diverter is not turning as it should. It will turn to the upper position during the fill, but then returns to the lower position for the remainder of the cycle. I also have no error code, which I thought was odd. I'm guessing this is either a problem with the microswitch or possibly the control board. How do I test for issues with one or the other? Thanks in advance.