It may be the WMS is blocked, i get AL5 or AL6 at the start of the program. here is how i have fixed it the last couple of times. WMS is around £70 (in 2010) - i have that on mine every 4yrs or son - i change the WMS sometimes called the water management system or water softener. it located on the left of the machine. the floor will get wet during this repair.
you need to turn off the power; turn off the water supply; to it take the top off remove the two screws at the back of the lid. then work your way around the left hand side removing the panel retaining screws. once that is off you can see a large blue plastic 'thing' this is the WMS that you need to replace. to remove this you need to remove the screws around the inlet for the water, i think there are 5 or 6, some are revealed once cover plates are removed. there are 5 or 6 retaining the WMS; the most important are the tow at the bottom toward the middle. now gently prise off the WMS releasing the tabs and catches. do not pull it off as there are some connections still to be disconnected. As to lift the WSM at the bottom right, behind the WMS there are three pipes held on with spring clips, these need to be released. then the WMS should lift off.. replacing is the reverse of the above. i did not find it too difficult other than the last bit with the pipes but you know your abilities. Good Luck