Conditions for Running the DTC

WARNING: This page is about a different car, the 2011 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.

P0403, P0404, P0405, P0406, P042E

The Ignition 1 Signal parameter is between 9-18 volts.
The engine is cranking or running.
The DTC P0401 intrusive test is not active.
These DTCs run continuously once the above conditions are met.

P0404

The EGR valve is commanded open.
DTC P0641 and P0651 are not set.

P0405

DTC P0641 and P0651 are not set.

P0406

DTC P0641 and P0651 are not set.
The EGR valve is not being commanded with a scan tool.

P042E

DTC P0641 and P0651 are not set.