Honeywell Standby Generators Error Codes

Air Filter Restriction

Controller displays 'Air Filter' or maintenance reminder; engine may run rich or lack power.

Restricted engine air intake

Auxiliary Shutdown

Controller shows 'Aux Shutdown', 'External Shutdown', or similar; generator will not start.

External safety or shutdown input active

Battery Charger Failure

Controller indicates 'Charger Failure' or battery does not maintain charge despite normal operation.

Onboard battery charger not supplying proper float voltage

Coolant Temperature Sensor Fault

Liquid-cooled unit shows 'Coolant Temp Sensor Fault' or erratic temperature readings.

Faulty or open/shorted coolant temperature sensor circuit

Emergency Stop Active

Controller indicates 'E-Stop Active' or similar and prevents starting.

Emergency stop circuit open

Field Sense Loss

Controller displays 'Field Sense Loss' or 'Loss of AC Sensing'; generator may run but not produce power.

Loss of alternator field or AC output sensing

High Engine Temperature

Generator shuts down during operation and displays 'High Temp' or 'Overtemperature' alarm.

Engine overheating protection trip

Ignition Fault

Controller logs 'Ignition Fault' or similar; engine cranks but does not fire.

Ignition system failure during crank

Low Battery

Controller displays 'Low Battery' or 'Battery Problem'; generator may crank slowly or not at all.

Insufficient DC voltage for starting and control

Low Coolant Level

On liquid-cooled Honeywell standby generators, controller displays 'Low Coolant' and prevents operation.

Coolant level below sensor threshold

Low Fuel Pressure

Controller displays 'Low Fuel Pressure' or similar fuel pressure alarm and the generator will not run or drops out under load.

Fuel supply pressure below minimum threshold

Low Oil

Controller displays 'Low Oil' or similar message and prevents the generator from starting.

Engine oil level below minimum sensor threshold

Low Oil Pressure

Generator shuts down shortly after starting and displays 'Low Oil Pressure' or oil pressure alarm.

Engine lubrication pressure below safe limit

Maintenance Due

Controller shows 'Maintenance Due', 'Service Soon', or similar reminder; generator still operates normally.

Scheduled maintenance interval reached

Overcrank

Generator attempts to start multiple times but fails and then shuts down with 'Overcrank' displayed on the controller.

Failure to start within allowed crank cycles

Overcrank - Low Fuel Pressure

Generator fails to start and displays Overcrank, and fuel pressure at the inlet test port is below specification.

Insufficient gas pressure during crank

Overcurrent

Controller logs 'Overcurrent' or similar fault and shuts down the generator even if the breaker does not trip.

Current draw above controller threshold

Overfrequency

Controller displays 'Overfrequency' or 'High Hz'; generator may disconnect from load.

Output frequency above nominal (e.g., above 61 Hz on a 60 Hz system)

Overload

Generator shuts down or trips its internal breaker with 'Overload' or 'Load Shed' message when large loads are applied.

Electrical load exceeding generator capacity

Overspeed

Generator starts and then shuts down with 'Overspeed' displayed; engine RPM is detected above normal operating range.

Engine speed exceeding controller limit

Overvoltage

Controller displays 'Overvoltage' and may shut down the generator; measured output voltage is above nominal (e.g., above 130V L-N on a 120V system).

AC output voltage above controller limit

RPM Sense Loss

Generator shuts down with 'RPM Sense Loss' or similar; controller cannot detect engine speed signal.

Loss of engine speed feedback to controller

Starter Fault

Controller displays 'Starter Fault'; engine does not crank or cranks intermittently.

Failure in starter motor or engagement circuit

Starter Lockout

Controller shows 'Starter Lockout' and will not attempt to crank after repeated failed starts.

Controller lockout after multiple unsuccessful crank attempts

Underfrequency

Controller shows 'Underfrequency' or 'Low Hz'; transfer switch may drop load.

Output frequency below nominal (e.g., below 59 Hz on a 60 Hz system)

Underspeed

Generator runs sluggishly, may stall under load, and displays 'Underspeed' or low frequency alarm.

Engine speed below required operating RPM

Undervoltage

Generator runs but output voltage is low; controller may show 'Undervoltage' or transfer switch refuses to transfer load.

AC output voltage below acceptable range

Symptom

Controller buttons unresponsive or intermittent

Keypad or user interface failure

Symptom

Controller display is blank or unreadable

Control panel power or display failure

Symptom

Corrosion on battery terminals and internal metal surfaces

Corrosive environment damage

Symptom

Fuel smell around generator enclosure

Gas leak or improper combustion

Symptom

Generator does not exercise at scheduled time

Exercise timer or schedule malfunction

Symptom

Generator is excessively loud or has abnormal knocking noise

Abnormal engine mechanical noise

Symptom

Generator runs but does not transfer power to the house

Automatic transfer switch (ATS) failure to transfer load

Symptom

Generator runs rough, surges, or hunts at no load

Unstable engine speed at light load

Symptom

Generator stalls when large loads are applied

Engine unable to sustain load

Symptom

Generator starts and stops repeatedly without load

Hunting or cycling start/stop behavior

Symptom

Generator transfers power but drops out or chatters under load

Unstable transfer switch operation under load

Symptom

Generator vibrates excessively during operation

Excessive vibration or imbalance

Symptom

Generator will not start in AUTO mode but starts manually

Auto-start control circuit failure

Symptom

Oil leak under generator

External engine oil leakage

Symptom

Soot or black residue around exhaust outlet

Rich fuel mixture or incomplete combustion

Symptom

Water pooling inside generator enclosure

Water intrusion into enclosure