Seems a little backwards to me. The ECU is looking for a signal from the sensor not the other way around. Check the connections at the sensor and where ever else you can see. Chances are the mechanic dislodged, damaged something, left something unplugged.
'11 F15.0 SCREW, 3.73, 6.5' Box, XLT XTR Candy Red. 4X4.