Fault Codes/Generac/21Generac21UnclassifiedStartingWhat This Code MeansThe ignition fails to spark; The ignition quits sparking; Not enough outputs on the ignition module for the cylinder setupPossible Causes•The signal relationship between the CAM and crank is out of sync.•Nexus setup to run a 10 cylinder with a 6 output ignition module.Related Generac Fault Codes222320241925182717281630Browse all Generac fault codes→ASK RUDY ABOUT THIS FAULTGet a diagnosis walkthrough for 21 on your specific Generac unit — cited to the OEM manual, not a forum guess.TRY IT FREE