Fault Codes/Rehlko/1239 31Rehlko1239 31UnclassifiedFuelWhat This Code MeansFuel leak; Supply voltage out of rangePossible Causes•Common rail leakage•Common rail leakage sensorRelated Rehlko Fault CodesDEF QUALITY ALERTDERATE WARNING1239 11DTC1239 0K0691662 0KD27V12661 8NOX FAULT661 5661 4Browse all Rehlko fault codes→ASK RUDY ABOUT THIS FAULTGet a diagnosis walkthrough for 1239 31 on your specific Rehlko unit — cited to the OEM manual, not a forum guess.TRY IT FREE