I determined that the circulation pump had failed because the dishwasher would fill the sump area with water and drain it properly, but the circulation pump would only hum intermittently without pumping water to the spray arms. This simple troubleshooting revealed that electrical power was going to the main pump and drain pump when called for so it wasn't a controller / electrical issue, but a mechanical problem with the circulation pump. My deep dive into the disassembly of the pump confirmed the failure.
I would recommend for a less involved installation however, to purchase the entire pump and motor assembly as I did here. For only a few dollars more, you're getting the entire factory assembled components (less drain pump) and new seals, well worth it in my opinion.