I'm translating the interface texts of an industrial control panel software and got stuck on this one. The module I'm referring to has some lists containing the sensors and switches for the digital and analog inputs and outputs of the machine. This module was called "Manual Control" in its current language but I've decided to give it a more proper term. In general those functions are mostly included in modules called "Diagnostics" in the plural form but when I've sent my suggestion to the software team they've decided to use the word in its singular form "Diagnostic".
I couldn't find any online reference to this matter so I'm asking it here. Which form is common and if possible could you explain why is it so?