How do I solve "A-3" on my Hotpoint Aquarius dishwasher?

When "A-3" flashes on the Hotpoint Aquarius dishwasher in the timer slot this apparently means that the outlet is blocked. How do I unblock this outlet already having taken out the filter to check this is OK and taken out the aluminium plate around the filter to swirl my hand inside the hole to check whether there is any debris. Sometimes it works alright, and sometimes not. Could this be anything resulting from the weather we are currently experiencing i.e. frozen something or other.