Did you order new sensors, and did the mechanic replace them? Once the get the light, your sensors are no longer reusable. You need to replace them with new ones.
If that is all done, my understanding is that the procedure is as follows:
1. Turn key forward to the ON position (without starting the engine)
2. Let sit for 2 mins.
3. Turn off.
I've read in some places that the driver's side door should be left open while doing this.
Please let us know if this worked!