Faulty Exhaust Gas Recirculation (EGR) valve
Carbon blockage of the pintle
Engine Light ON (or Service Engine Soon Warning Light)
Code P1406 Buick Description
The Powertrain Control Module (PCM) determines that the EGR valve is stuck open if the actual Exhaust Gas Recirculation (EGR) position and the learned closed EGR position vary by more than a predetermined value. The PCM tests for a stuck valve when the desired EGR position is at 0%. The PCM commands the EGR valve to 100% during certain driving conditions in order to clear a possible restriction from the EGR valve if the PCM determines that the valve is stuck open.
P1406 Buick Code – EGR Valve Pintle Position Circuit