Dishwasher: Zanussi DE6965 - AL5 alarm code

Alarm code after 4- 5 mins from start of cycles. Book says check input hose and filter for blockage. All clear and clean and mains pressure ok. Buzzing noise from input hose connction area + feel vibration through input hose - Is this the input valve stuck? If it is likely, how do I check this out? Machine is 4yr old.

The drain pump is working. The fault started off semi-permanent, - water would flow but cycle terminated after several minutes (with AL5 flashing). After a few hours, with the machine being moved in and out a couple of times, input hose being checked, mains plug being disconnected in case the firmware logic had gliched and half dozen attempts at starting cycles on different programmes, the fault went permanent - i.e no water input and cycle termination after several minutes.

Could be a faulty valve. More likely valve is locked out due to internal blockages. If machine thinks it's overfilling (blockage stopping water from entering machine fast enough) water pressures up an overflow pipe to the top of the valve which shuts the valve. Turn off the water, disconnect the inlet hose at the valve on the machine, let it drain, refit hose, turn on water and see if the machine fills. If it does start to fill then it's a blockage internally.

Sleepyhead

I followed your advice: - Yes, the m/c did start to fill with water, hence dispelling the dead valve theory. It went on to complete a cycle. I then ran two more cycles with success. Looks like whatever was causing an intenal blockage (or air pocket?) which presumably shut the valve by the pressure diaphram switch, cleared when I disconnected the outflow pipe from the valve.
One other possibility? ----
On the night the fault occurred, a cycle had completed leaving the end-of-cycle leds on all night. During the night there was an electrical storm.
In the past, I've had video recorder functions corrupted by electrical storms, which needed the recorder to be disconnected from the mains to re-initialise the software. I originally thought this may have been the reason for the dishwasher malfunction, but when I unplugged and re-plugged it with no success I discounted it. However, the machine was subsequently left unplugged for nearly 24hrs before I tried your suggestion. So, the question is, - is there a battery backup in the machine which would store programme details for a relatively short time (say - less than 24hrs) in case of a power failure. If there is, then software corruption could account for the temporary malfuntion.

No battery backup. It's been a partial overfill or overfoaming that's locked out the valve. It's locked mechanically not electronically.