Cummins/Onan Onan Engine Engine

• VOLTAGE SENSE FAULT—CODE NO. 27 27
  Fix: See an authorized Onan dealer.
• UNDERVOLTAGE FAULT—CODE NO. 13 13
  Fix: Reduce the number of connected appliances, especially when air conditioners and battery chargers are running.
• UNDERFREQUENCY FAULT—CODE NO. 15 15
  Fix: Reduce the number of connected appliances, especially when air conditioners and battery chargers are running.
• There is no electrical power even though the genset runs.
  Fix: A. Reset tripped circuit breakers. See Powering Equipment. b. Unless there is an automatic power transfer switch, plug the boat power cord into the genset power output receptacle (if so equipped) or turn the boat power selector switch to its genset position (if so equipped).
• The remote battery condition meter indicates low voltage.
  Fix: A. Clean and tighten the positive (+) and negative (- ) battery cable connections at the battery and the genset. b. Recharge the battery. Refer to the battery manufacturer’s recommendations.
• The genset keeps stalling or the circuit breaker keeps tripping.
  Fix: Try running with fewer appliances connected. See Powering Equipment.
• The engine runs and then stops or surges.
  Fix: A. Check the fuel tank and fill if necessary. b. Check the engine oil level and add oil as necessary. Drain excess oil if the level is above the dipstick Full mark. c. Check and reset the carburetor altitude adjust knob. See Varying Operating Conditions. (Gasoline models only.) d. Secure the spark plug lead on the spark plug. e. Replace the spark plug.
• The engine fails to crank.
  Fix: A. Try starting at the genset rather than at the remote control. b. Replace the fuse on the control panel if it has blown. c. Clean and tighten the positive (+) and negative (- ) battery cable connections at the battery and the genset. d. Recharge the battery. Refer to the battery manufacturer’s recommendations.
• The engine cranks slowly.
  Fix: A. Disconnect the air conditioner and other large loads. b. Clean and tighten the positive (+) and negative (- ) battery cable connections at the battery and the genset. c. Recharge the battery. Refer to the battery manufacturer’s recommendations. d. Change the engine oil to oil having the proper viscosity for the ambient temperature. See Table 1.
• The engine cranks but fails to start.
  Fix: A. Check the fuel tank and fill if necessary. b. Open any closed fuel shut off valve. c. Check engine oil level and add oil as necessary. d. Service the air cleaner. e. Secure the spark plug lead on the spark plug. f. Replace the spark plug.
• SPEED SENSE FAULT—Controller unable to sense quadrature frequency CODE NO. 45
  Fix: See an authorized Onan dealer.
• SERVICE CHECK FAULT—CODE NO. 3 3
  Fix: Check the second-level fault code by pressing STOP once. The second-level fault code will have two-digits. The faults are listed in numerical order in this table.
• PROCESSOR FAULT—Microprocessor ROM error during self-test CODE NO. 42
  Fix: See an authorized Onan dealer.
• PROCESSOR FAULT—Microprocessor RAM error during self-test CODE NO. 43
  Fix: See an authorized Onan dealer.
• OVERVOLTAGE FAULT—CODE NO. 12 12
  Fix: See an authorized Onan dealer.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan Onan.

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.