nakturk wrote:But since I have no idea about a relay, I don't know what to do now, any clues please ?
As a second question, if I need to replace it, how should I search it (ie. how a relay named ? number, capacity ?)
I don't have a part number for you. I'd go to someplace like mouser.com (no minimum order) and look for a 12v coil relay with contacts to handle 10 amps. SPDT like OEM. Then extend all five (?) lines from the DPC Module to the relay. IOW, desolder the OEM relay, solder on five wires in its place (preferably in differing colors) and run them to the appropriate places on the replacement relay.
AFAIK, there is no "drop-in" replacement that will solder to the OEM board.
I did exactly what I describe above to my diesel Sentra's GP controller to restore afterglow when its relay crapped out like yours. Good pics: see
this post.
Your sanding of the remains of the contacts will
not last.
If you don't think that you're up to that job, I can do it for you, but it'll be a lot cheaper if you do it yourself (unless you cross-wire something). PM me if you need my help.