300m scan-code P0406 ? Cause?
 

Yesterday my '00 300m was showing the check-engine light on instrument panel (possibly for the first time ever). Using the ignition-key method, the panel displayed 2 codes:

P1684
P0406

The first one has to do with the battery being disconnected - but I think is supposed to go away after 50 starts? I did replace the ->factory original<- battery a couple months ago (how is that for the original battery? 1 month shy of 12 years?). Does the 1684 code normally turn on the engine light?

The second code (P0406) is either caused by the EGR valve or the gas-cap. I did fill the tank right up and then drive about 100 miles the day before the light came on, so on a hunch I took the cap off and put it back on yesterday, and later that night after a few short trips the light went off.

Anyone know anything definite about if any combination of tank-fill level, ambient temperature, a highway drive or a loose gas cap can cause the P0406 code on a 300m ?

455 would be the gas cap not 406 code numbers do not bleed over into different systems