I've had the dreaded EGR 'check engine' problem for a month or more. In all that time the dash 'check engine' light has been lit, even when I've repeatedly cleared it with the scanguage, it would return within minutes of driving anywhere. I never ready got around to cleaning or replacing the EGR valve.
But yesterday I topped up my lead/acid battery and charged it. Since then I've cleared the EGR codes (1404, 404 if I remember correctly) and they haven't returned. So fingers crossed the EGR codes might have been just a low battery problem (i guess with everything considered that value may just be current sensitive).
If anyone has a similar EGR problem try simply charging the battery but remember to top up with demin water first.