Hi. You most likely need an egr valve. The contacts inside for the electrical solenoid go bad.
The labor usaully is about 1.5hrs. labor times the labor rate at the most.
The part is about $150.00.
Here is some info and the other possiblities for this, but 99.9% it's the egr valve.
P0406 - EGR POSITION SENSOR HIGH
When Monitored: With the ignition on. Battery voltage greater than 10 volts.
Set Condition: EGR position sensor signal is greater than 4.89. One trip Fault.
EGR POSITION SENSOR SIGNAL CIRCUIT OPEN
EGR POSITION SENSOR SWEEP
EGR POSITION SENSOR SIGNAL CIRCUIT SHORTED TO 5 VOLT SUPPLY CIRCUIT
EGR POSITION SENSOR SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
EGR SOLENOID ASSEMBLY INTERNAL FAILURE
SENSOR GROUND CIRCUIT OPEN