Bosch DW continues after timeout

I saw a similar, previous post but can’t find it again. The reply was "probably the control board." The troubleshooting guide says it may be water temp too low. I know how to check the water temp. But how can I verify the problem is the control board? (Don’t want to buy a board if I don’t need it.)

Additional symptom: In order to start the dw, the power has to be turned off, then on, then choose cycle.

Thanks for your help!
Richard in AZ