Fault Codes/Cummins/H669CumminsH669UnclassifiedGeneralWhat This Code MeansEquipment shutdownPossible Causes•Low coolant levelRelated Cummins Fault CodesH706L028H389OFFH268OVER SPEEDFAIL-TO-SYNCHRONIZE WARNINGRED − FLASHINGE153SERVICE DUEE125E089Browse all Cummins fault codes→ASK RUDY ABOUT THIS FAULTGet a diagnosis walkthrough for H669 on your specific Cummins unit — cited to the OEM manual, not a forum guess.TRY IT FREE