Bosch Dishwasher E04 error code

6yo Bosch Exxcel Aquastar 6.5L repeatedly showing the E04 error. Seems to get most of the way through a wash cycle before error occurs.

According to advice on this page I checked and cleaned the spray arms, and found nothing blocking any of the holes. I have also checked the drain filter and impeller which is clear. Drain is not kinked and working fine. Turned off for >20m at plug to reset multiple times. When running a test cycle with dishwasher empty I opened to check and noticed that the water is cold even after the detergent drawer has opened, running on an intensive cycle.

According to all the advice the issue is a faulty flow sensor (like this one I think), but I'm concerned that the water is not heating up at all and if something else is the problem. Any ideas or do I need to contact a pro, or just bite the bullet and buy a new one? TIA

The error code does indicate a faulty flow sensor , as you have checked all the arms and found nothing I would replace it

You will probably find that the cold water is linked to the flow sensor and replacing it will solve this

Check its draining away ok.

The waste can get blocked where it meets the rest of the plumbing.