Fault Codes/Cummins/O/EXCCumminsO/EXCUnclassifiedGeneralWhat This Code MeansLED lights in O/EXC conditionRelated Cummins Fault CodesO/VOLTSOFFL028OVER SPEEDH706PUT CONFIGURATION ERRORH669RED − FLASHINGH389SERVICE DUEH268UFROBrowse all Cummins fault codes→ASK RUDY ABOUT THIS FAULTGet a diagnosis walkthrough for O/EXC on your specific Cummins unit — cited to the OEM manual, not a forum guess.Your question about O/EXCGET THE ANSWERFree account required — we'll bring your question with you.