First I heard also.
It could be the oil pressure sensor is bad.
Since you have the GT with NAVI, you can go into the NAVI's test mode and scan out the
OBDII error code w/o external device.
Search the How-To forum for a thread I posted for the procedure.
Once you find the code, you can do a simple googling and find the description.
(actually, that is the first thing dealer's mechanic does when there is a light -> find the code -> find the description).