Disassemble the pump to access the chopper as described in the Tech sheet
(Chopper/Filter service) and check for a stuck foreign objects or broken chopper.
If there is nothing wrong, then the motor or the whole pump & motor assembly has to be replaced. The difference in price between the motor and whole assembly is about $20, but the whole new assembly will make the repair much more reliable and it is easier to replace.
If you can do it yourself, then it's probably worth to fix it. If you have to hire somebody, then it's probably better to get a new dishwasher.
- The motor Part number: AP3179651
- The pump and motor assembly Part number: AP4434617
Here are the breakdown diagrams and Replacement parts for WHIRLPOOL GU1500XTKQ0 Undercounter Dishwasher | AppliancePartsPros.com