Question

on the techwrench, the \u\ button serves what function?
change to the desired torque unit
increase the torque value
power on and off
to activate the \peak\ torque mode

Explanation:

Without specific information about the Techwrench, this is based on common functionality associations. The "U" button is likely related to units for torque - related tools. Changing torque units is a common function that could be assigned to a single - letter button.

Answer:

Change to the desired torque unit