Climate control low setting only not working

Not sure if it's a new problem or I just never noticed, bought the 2015 a year ago, and just noticed that on "low" there's nothing. The remaining settings up to high work fine. "Off" is the same as low and I can feel the detent position between all settings when I turn the knob. I pulled the knob and it's in the correct orientation, flat edge of the knob spindle points to low, off etc. I'm not sure how the electrical for the knob and blower work, how the low setting would be an independent switch...doesn't make a lot of sense.

 

Get a test light and start checking.
https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/#post-28042158