Really confused by PAS fault - advice really needed!

I'm very confused - anyone got any advice?

I had all the usual problems with the flickering lights and intermitent PAS. I changed the steering angle sensor and it all worked perfectly - for two weeks.

Then the light came on and for the last three days, all for one quick journey on the first day of noticing it, it has stayed on. A complete pain.

I have taken the sensor out again and given it a quick clean and put it back in ensuring the connections were tight. But no joy.

Does anyone know what could be wrong? I have wondered about the ECU needing ressetting and the fault being cleared, or horror of horrors a fault with the pump. But that would not explain why it all worked perfectly for two weeks, including a long run from West Yorkshire up to Keswick in the Lake District and back.

Any help would be much appreciated