Gaggenau dishwasher runs very long

We have a Gaggenau dishwasher model GM915-710. It is about 5 years old. It normally takes 90 minutes for a cycle (the last 10 minutes of the cycle are when it is drying).
I have noticed lately that the time remaining display will count down to 1 minute and then sit there for at least another hour with water sloshing around even though it should have been drying long before then. It does eventually finish and dry, but it takes forever....Yesterday, it took about 3-4 hours to finish its cycle. Does anyone have any ideas why this would be? Our DHW temp is 130 degrees.

 

The thermistor that checks the temp is not reading correctly and the dishwasher goes to a longer default setting that is programed in the board... Replacin it should take care of it

 

Thanks. The Gaggenau people had told me it was probably the timer. Is there any way to test the thermistor to see if that is the problem? Are there any online repair manuals for this dishwasher?

 

I have not found any but there should be a wire diagram behind the lower kick panel withe the resistance checks