Excellent Pic there showing the burnt contacts - I have been getting the code for over 6 months now and its just been annoying the hell out of me.

Ive checked the pcb before and all the solder joints were fine, check valve was fine and no other obvious causes until today I opened the relay box up again and looked at the contacts and there it was - a filthy black contact. I got some wet and dry paper and slid it between the contacts to clean them up - placed the relay back and no CEL!! So far so good anyway but that was definitely the problem. Its a difficult one to spot!