Does Sentry Pro cause phantom or parasitic drain while my Tesla is parked?

Not on its own. Sentry Pro does not poll your Tesla and adds no meaningful drain while the car is parked: data arrives by push over Tesla Fleet Telemetry, only while the car is already awake, and opening the app sends the car no wake-up command.

Phantom drain is battery your car loses while parked and doing nothing you asked it to do. The two things that can wake a sleeping car are actions you take: turning Sentry Mode on from Sentry Pro and a Schedule Sentry Mode ON time, both of which send a wake-up before the Sentry Mode command (two wake attempts per account per 24 hours).

If you are seeing drain while parked, the usual sources are:

• Sentry Mode itself, which independent tests and owner logs mostly put at roughly 130–250 W (Tesla publishes no figure)
• The Tesla app or its home screen widget waking the car
• An open live camera feed
• A phone key sitting at the edge of Bluetooth range
• Tesla’s own data sharing upload

Apart from turning Sentry Mode on yourself, the one Sentry Pro feature that sends anything to the car is Schedule Sentry Mode, and its net effect is to reduce drain by turning Sentry Mode off for part of the day.

For the full mechanism, see Will Sentry Pro wake up my car and consume battery power. For measured figures, see How Much Battery Does Sentry Mode Use?. For everything else that keeps a parked Tesla awake, see Tesla phantom drain: what’s normal and what to switch off.