Were is the location for the sensor a p0406

Question

Any location for sensor a an my expedition

Answer 1

P0406 Exhaust Gas Recirculation Sensor "A" circuit high

There a difference between a Sensor "A" and Circuit "A".You have a code for circuit "A" this is the reference voltage, The ECM monitor the voltage and see nothing in return. You either have a disconnection of the EGR vlave, or the EGR itself.