Diplomat Wpl D/w

This one is intermittant, but when it does fail
Rinse prog light (1st one) is on and start light flashes 4 times.

I have looked at fault codes and indicates pump, pcb or owi (water indicator)

The appliance is clean inside regular cleaners flushed through, will work on short 30 min wash no problem only seems to happen on 65 wash.
but not every time.?

Drain pump just runs continously then errors out with above code.
Drainage clear no restrictions, reset it works on rinse ok, heating ok, dispenser relaeasing and washing normally although it has crap askol circ pump thats ok?

What is and where is the OWI water indicator. 😳

The only problems on these i usually have had is diaphram switch full of crap, that appears ok (maybe weak switch)? and thermistor, the odd flow meter.

Cheers Steven