I'm new to the forum - I have 2008 Chev 2500HD LMM. Last year had the fuel rails, fuel lines, hi and low fuel pumps, multiple sensors and ecm replaced by local dusk shop due to getting bad diesel while out of town. After that, mileage was horrible and system wasn't performing correctly. I took it to dealership to program correctly. Drive it home Thursday evening. Went to start it this morning and it turns over, but won't start. Code 2454 on scanner. How do i determine if DPF sensor is bad? Or something else?