Dishwasher fails, with continual beeps?

Mt diplomat machine fails part way through its cycle. When it stops it stops with a beeping sound coninuous until i reset, prior to resetting I have noted that the start cycle light is flashing 3 times with a slight pause the 3 times again, this is continuous until i reset. I have since added rinse aid, salt and tried it on a 70c wash...machine fails the same way on each occasion....I think the machine is failing due to the water not heating?? please advise.