2011 Nissan Sentra knoking noise

have a local pro check this for a bad belt tensioner

I've been searching for this answer for MONTHS now... I read it was the ABS (anti-lock brake system) "recharging"... the dealer also said this is the issue and that it was "normal". I suspect otherwise. I have a 2012 Sentra SE-R and its plagued with noise issues. The noise sounds like a knock, but is related to the brakes. They told me that when you leave the car off for a period of time, the ABS pressure goes down, then when you start it, it builds back up, and what I hear is the pump. It didn't start doing it until a few months ago. I also think they know why it happens and wont admit its a build issue. Ill never buy another Nissan again.

you are correct here is the tsb on it. sorry I didn't catch this for you.
NOTE:This bulletin has been amended to include vehicles with 30 MPH Self-Check logic. Discard previous bulletin.

If you identify:
Clicking, knocking, clunking, buzzing, or thumping noise coming from the engine compartment area.
And:
The noise occurs only once per ignition cycle (ignition OFF > ON) and does not occur again until the ignition is cycled.
And:
The noise happens briefly for only a few seconds on acceleration, between 5 and 30 MPH; depending on vehicle model and year.
The above condition is normal, may be louder if the vehicle has not been operated for a prolonged period of time, and does not need repair.
Each time the ignition is turned on and the vehicle reaches approximately 5 to 30 MPH, the ABS/VDC system performs a "Self-Check" to confirm components of the ABS/VDC system are operating correctly.
This Self-Check function creates the noise described above.
If the brakes are being applied when the Self-Check occurs, a vibration may be felt in the brake pedal and an increased level of noise may be noticed