Run the extended version of the Apple Hardware Test. Sometimes you will get an error if you run the quick version, and it may be something of a false positive. Some have found doing an SMC reset 3 or 4X can eliminate the error (note: a work around not a fix). If it is indeed a logic board error it points to a sensor(s) failing, VPOR might be VGC(VPU) related. You'll probably need a new logic board, AFAIK sensors as well as the VGC are soldered to the logic board which pretty much makes them non-DIY repairs, as soldering on logic boards are not for amateurs.