Also, check the sprinklers for any clogging.; We have had babies for the past few years and cotton wool seems to get everywhere; If a small bit gets into a dishwasher, it doesn't disintegrate but ends up in the sprinkler holes. The sprinkler heads pop off and can be easily picked clean.
We have a seven year old machine and we recently got it serviced, as it was giving some trouble. I was very surprised that anyone would come out to do this for a reasonable sum (€68), but a man called out, ripped the machine apart, cleaned out a LOT of hard greasy stuff, put it back together and was gone within a half an hour. We got him through the "Customer Care line" for our particular machine (siemens or bosch I think) which was a first for me - I had always assumed that these care lines are staffed by people who really don't care.