Conditions for Running the DTC

WARNING: This page is about a different car, the 2009 Pontiac Torrent and 2009 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.

P0403, P0404, P0405, P0406, P042E

DTC P0641 or P0651 are not set.
The Ignition 1 Signal parameter is between 11-18 volts.
The engine is cranking or running.
The DTC P0401 intrusive test is not active.
These DTCs run continuously when the above conditions are met.

P0404

The EGR valve is commanded open.
ECT is more than 75°C (167°F).

P0406

The EGR valve is not being commanded with a scan tool.
ECT is more than 75°C (167°F).

P042E

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