considering 2002 4Runner - how to check 4wd

My son is considering buying a 2002 4Runner but is not local right now. So I am his inspector. Does anyone have a practical way to check out 4 High? Besides looking for a solid "4wd" light (not flashing), how can I ensure things are working properly without taking it to a mechanic? Just FYI - the 4Runner goes into 4 Low OK and I can definitely tell that it's in 4 Low. Thanks for the help.

 

If it goes into 4 lo 4 hi works. It has to shift into 4wd before low range can be engaged.

 

Thank you so much. The light was flashing when I test drove it, and now the seller said he replaced a sensor and all is good. I just want to minimize my $$ risk here before buying. Thanks again!