replaced ecu

I am not sure which module yo have replaced. A vehicle equipped with the Cummings Diesel has (2) modules, One is the Powertrain Control Module (PCM) mounted on the right firewall area and the 2nd is the Cummings Engine Control Module (ECM) mounted on the left side of the engine block. You should take your vehicle to your local dealership and have them perform a diagnostic check as there may be PCM or ECM software updates that can only be performed by the dealership.