ACE wiring problems ?

Hello
I'm lost with this problem and don't find any mechanic who can help me. My Discovery 2 is with ACE and from time to time I was getting the amber light, which now is active always when I start the car, but sometimes when I wash the car the light comes out until the car dryers a little bit and then comes again. Launch diagnostics shows no real data about ACE, engine speed, pressure sensors are all on N/A. I have a list of faul codes about low pressure and main relay issue. Tried to check all fuses and ACE relay and they are good. Maybe someone has an idea from where start ?

Start with applying a bit of thought to your problem - what does water do to the conductive properties of anything?

Once you've worked out that it increases conductivity, then you're on the way to start looking for the problem - water is getting into a corroded wire and 'improving' the circuit.

Once you get that far, look at which circuits involved are likely to be affected - ideally using a circuit diagram.