How can you fix obd 2 code p0405?

P0405 EGR Sensor A Circuit Low

Causes
Short to ground in EGR signal or Reference circuits
Short to voltage in EGR ground or signal circuits
Bad EGR valve
Bad PCM wiring issues due to chafing or loose terminals

EGR valves get a lot of nasty gases passed through them, sometimes fixing the issue involves a good cleaning, others mean replacing the valve, cold weather can cause intermittent codes as well.

Use a scan tool to operate the valve, if it does not respond try checking for voltage at the connector.