2002 rsx need help with P1259

hi all,
helping out a buddie, Engine Light came on out of the blue. he didnt change the oil or anything. Rpm wont go over 3000-4000rpms? limp mode.
looks like his oil pressure switch or vtec seloniod?

how to fix this problem? anyone had a similar problem? whats the location of that oil pressure switch that triggers the vtec?

thanks. searched but to no luck.