How to fix an F1 error code on a Fisher Paykal Model DD603 dish drawer?

We started receiving an F1 error code at about 3 AM one morning when the dishwaser was not even in use. I removed both tubs and turned them on their sides to see if there was excess water in them. There was only a little residual in each of them. After plugging the machine back in and turning on the water, I was able to run through a 10 minute rinse cycle with no problem, however, a few minutes after the rinse cycle had completed I started receiving the F1 error message again.
Any ideas?