93 Mpv hold light on trans

Hello , I am hoping someone out there might know what would cause the hold feature on a mpv to stay on and not allow it to shift to a higher gear. It is my brothers van and he lives accross the country from me so I do not have access to the vehicle for testing. Any help is greatly appreciated. I am mostly a gm product owner and so my knowledge is mostly them. I figure it is a sensor on the trans but not sure where to look and he does not have a scan tool and dont know if there is a way read the codes without one on Mazda's.