There is no relay, everything is done in an electronics board which is located
in the roof box where the front interior lights, clock & open door indicators
are. You have to remove the transparent cover of the triple light by a flat
screwdriver and find the two screws below (well, above in this case...). Here is
the magic, but don't ask me for P/N, take it to your local electronics hacker...
There is also a receiver for the factory remote lock there, so be careful not to
mix bananas and apples.