Operator’s Manual Vehicle Maintenance CXU, CHU, GU, TD, MRU and LEU 11 Engine Control, EGR and Fuel Systems Acts that constitute tampering with Engine Control, EGR and Fuel Systems: Removing rendering inoperative, or modifying the engine control system such as the ECU, EGR system components, or fuel system components, in order to allow the engine to operate outside of the manufacturers specifications is not allowed and violates both warranty and legislation.