First Tacoma, A/T Temp light already on

Hey all thanks for the add! New to trucks, 4x4 and Toyotas, but ready willing and able to learn if this group fosters newcomers! So I recently picked up a 2003 Tacoma TRD Off-Road, 4x4 auto trans. Everything seems good at 167k miles but I noticed when shifting into 4 low (don't remember if it did this in 4h) the a/t oil temp light comes on (along with abs but that's normal) and goes off when I go out of 4L. Light wasn't on while driving in 2wd nor when I parked. Coolant is a smidge low and tranny fluid looked clean, red and didn't smell burnt. Any suggestions? Thanks!

 

Anyone?