P0405 Buick Exhaust Gas Recirculation Position Sensor Circuit Low Voltage

P0406 Buick Exhaust Gas Recirculation Temperature Sensor Circuit High Input

Possible causes
– EGR Valve clogged, dirty or leaky
– EGR valve damaged/defective
– EGR volume control solenoid valve
– EGR temperature sensor and circuit
– EGR volume control solenoid valve harness is open or shorted
– EGR volume control solenoid valve circuit poor electrical connection
What about the obd code?
An improper voltage signal is sent to ECM through the valve
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
– Engine hesitation
P0406 Buick Description

Early Exhaust Gas Recirculation (EGR) systems component s include and EGR Valve, and Engine Control