Can there be codes without the CHECK ENGINE LIGHT?

I November of 2005 all the fuel lines with the o-ring were replaced.

I was thinking of trying a diesel purge. If that does not take care of it I will likely go to the dealership and then sell this POS. For me the negatives of this car far outway and positives. With this car I am always waitng for the 'other shoe to drop' and I am tired of it. No more post W124, W126, or W201 Mercedes for me.