Fault Codes/Cummins/243Cummins243UnclassifiedCoolingWhat This Code MeansAmbient temperature sensor reading out of rangePossible Causes•Ambient temperature sensor output is out of range (OOR), high or lowRelated Cummins Fault Codes2482492423432413532404152354882031222Browse all Cummins fault codes→ASK RUDY ABOUT THIS FAULTGet a diagnosis walkthrough for 243 on your specific Cummins unit — cited to the OEM manual, not a forum guess.Your question about 243GET THE ANSWERFree account required — we'll bring your question with you.