Vehicle active Scanners only highlight players while the module is active, and in the modules scan area.

I propose that infantry active Scanners work similarly: Active scanner only works while it is the active equipment, like a cloaking device
Swap to active scanner, tap r1 to engage the scanner. The scanner then continuously scans for its scan duration, only highlighting things while they are in its cone of effect.
If the scanner is deactivated or its scan duration ends, it enters a full cooldown.