Onan Standby Generators Error Codes

Code 11

Generator cranks but will not start; fault light on, Code 11 displayed or flashed

No Crank Signal / Start Command Fault

Code 12

Generator cranks but will not start; Code 12 displayed indicating low cranking speed

Low Cranking Speed / Low Battery Voltage

Code 13

Generator shuts down shortly after start; Code 13 displayed for governor actuator or speed control fault

Governor Actuator / Speed Control Failure

Code 14

Generator shuts down; Code 14 displayed indicating over-speed condition

Engine Overspeed Protection Trip

Code 15

Generator shuts down; Code 15 displayed for under-speed condition

Engine Underspeed / Load Too High

Code 19

Generator shuts down during crank or shortly after start; Code 19 displayed for governor actuator overcurrent

Governor Actuator Overcurrent / Short

Code 23

Generator shuts down; Code 23 displayed indicating low oil pressure

Low Oil Pressure Shutdown

Code 24

Generator shuts down; Code 24 displayed indicating high engine temperature

High Coolant Temperature / Overheat

Code 25

Generator shuts down; Code 25 displayed indicating high exhaust temperature

High Exhaust Temperature Shutdown

Code 27

Generator shuts down; Code 27 displayed indicating voltage sense loss or abnormal AC output

AC Voltage Sense Fault

Code 29

Generator shuts down; Code 29 displayed indicating low voltage output

Low AC Output Voltage

Code 31

Generator shuts down; Code 31 displayed indicating overspeed or frequency too high

High Frequency / Overspeed Fault

Code 32

Generator shuts down; Code 32 displayed indicating low cranking speed or failed to start

Failed to Start / Low Cranking Speed

Code 33

Generator shuts down; Code 33 displayed indicating overcrank (too many failed start attempts)

Overcrank / Failure to Start

Code 34

Generator shuts down; Code 34 displayed indicating low frequency

Low Frequency / Underspeed

Code 36

Generator shuts down; Code 36 displayed indicating engine stopped without shutdown command

Engine Stopped Unexpectedly

Code 37

Generator shuts down; Code 37 displayed indicating voltage imbalance or phase error (3-phase units)

Phase Voltage Imbalance / Phase Loss

Code 38

Generator shuts down; Code 38 displayed indicating overcurrent or short circuit

Overcurrent / Short Circuit Protection Trip

Code 41

Generator shuts down; Code 41 displayed indicating loss of engine speed signal

Loss of Engine Speed Signal

Code 42

Generator shuts down; Code 42 displayed indicating loss of field or excitation

Loss of Excitation / Field Circuit Fault

Code 43

Generator shuts down; Code 43 displayed indicating DC overvoltage

DC Bus Overvoltage

Code 44

Generator shuts down; Code 44 displayed indicating DC undervoltage

DC Bus Undervoltage / Low Battery

Code 45

Generator shuts down; Code 45 displayed indicating fuel level low (if equipped with level sensor)

Low Fuel Level Shutdown

Code 47

Generator shuts down; Code 47 displayed indicating fuel solenoid circuit fault

Fuel Shutoff Solenoid Circuit Failure

Code 51

Generator shuts down; Code 51 displayed indicating intake air heater fault (diesel units)

Intake Air Heater Circuit Failure

Code 54

Generator shuts down; Code 54 displayed indicating CAN communication fault (on newer digital models)

CAN Bus Communication Error

Symptom

Automatic transfer switch does not transfer load to generator when it is running

Transfer Switch Fails to Transfer

Symptom

Control panel display is dim, unreadable, or segments missing

Display / HMI Failure

Symptom

Fuel leak observed around generator, smell of fuel in enclosure

External Fuel Leak

Symptom

Generator battery repeatedly goes dead between exercise cycles or outages

Chronic Battery Discharge / Charging System Issue

Symptom

Generator cranks normally but does not fire or start, no specific code shown

No Start – Fuel or Ignition Failure

Symptom

Generator does not start automatically during a utility power outage, but starts manually

Auto-Start / Remote Start Failure

Symptom

Generator emits blue smoke from exhaust, especially under load

Oil Burning / Internal Engine Wear

Symptom

Generator emits excessive black smoke from exhaust during operation

Rich Fuel Mixture / Incomplete Combustion (Diesel or Gas)

Symptom

Generator emits white smoke, especially on startup

Incomplete Combustion / Coolant or Fuel Issue

Symptom

Generator enclosure becomes excessively hot, components show heat discoloration

Inadequate Ventilation / Cooling Airflow Restriction

Symptom

Generator is excessively noisy during operation (mechanical knocking or rattling)

Abnormal Mechanical Noise

Symptom

Generator produces power but voltage is unstable or fluctuates under load

Unstable Voltage Regulation

Symptom

Generator runs but does not produce AC power at the terminals

No AC Output / Loss of Excitation

Symptom

Generator runs but frequency (Hz) is too low or too high

Incorrect Engine Speed / Frequency Out of Spec

Symptom

Generator starts then shuts down after a few seconds, no load applied, no clear code

Run-Then-Stop – Safety Circuit or Fuel Issue

Symptom

Generator vibrates excessively, causing enclosure or nearby structures to shake

Excessive Vibration

Symptom

Generator will not start, no error code displayed, panel appears dead

No DC Power to Control Panel

Symptom

Oil leak visible under generator or on engine surfaces

External Engine Oil Leak

Symptom

Strong fuel odor around generator during or after operation, no visible leak

Fuel Vapor Leakage / Venting Issue