Conditions for Running the DTC: P0406

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

The EGR valve is not being commanded with a scan tool.

P042E

The ECT is more than 75°C (167°F).
The EGR Valve is commanded to 0 percent for 40 seconds after the EGR Valve has been commanded to 40 percent for 1 second.