Hello everyone, I am the service manager for a small company with about 15 trucks, mostly Ford's, but we do have three Chevy's that have done quite well thus far. Recently two of the trucks have started flashing the exact same code and it has me puzzled. The trucks are 2006 models with the 6.6L Duramax and the Allison tranny. The code that both of them are flashing is P2200, which comes up as NOx Sensor, Circ bank 1. Most of my experience is with the Ford PSD so I have gotten to do a lot of diagnostic work, I simply don't know much about the Duramax engine. Does anyone know what would set this code? I know it is part of the emissions system, but there has got to be something else that is part of the system causing it to set a DTC. I know I could always just send it to the dealer, but that would take all the fun out of it. Any help would be appreciated.