D - Air Restriction Indicator Light - will come on if air restriction indicator shows that air cleaner requires service.
Huh??
Instead of writing "air filter" below the dash light light they have a picture of who knows what that nobody can figure out. Why not words? Well it is not politically correct to discriminate against people that can't read a native language.
Ah-- now I get it!
Well, given they sell their equipment all over the world I would imagine if they had to use words customized for each country they export to that the price would have to increase accordingly.