Bosch Serie 4 dishwasher SMS50D08AU gives E04

[CharlieSierra]

Hi, as per the title, my Bosch dishwasher is not heating the water or drying properly, and gives an E04 error at the end of the cycle. I have tested the heat pump and the thermostat and heating element are both giving readings in the normal range on the multimeter. I've given the machine several good descales.

What else can I try? Thanks :)