Guardian
Guardian Standby Generators Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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AIR FILTER
Controller shows AIR FILTER or MAINTENANCE AIR FILTER; generator may run rich or lack power.
Restricted Air Intake – Maintenance Reminder
CHARGER FAIL
Controller shows CHARGER FAIL or BATTERY CHARGER FAULT; battery may not stay charged between exercises.
Integrated Battery Charger Failure
EMERGENCY STOP
Controller displays EMERGENCY STOP or E-STOP ACTIVE; generator will not start until cleared.
Emergency Stop Circuit Activated
ESTOP ACTIVE
Display shows ESTOP ACTIVE or REMOTE STOP; generator remains locked out.
Remote Emergency Stop or Shutdown Input Active
EXERCISE NOT RUN
Controller indicates EXERCISE NOT RUN or MISSED EXERCISE; generator has not performed its scheduled weekly test.
Missed Automatic Exercise Cycle
FUEL LEAK DETECTED
Controller or external sensor indicates FUEL LEAK or FUEL ALARM; fuel odor may be present near generator.
Fuel Leak Detection Alarm
GENERATOR FAILURE TO START
Controller logs FAILURE TO START or similar; unit never fires, only cranks or clicks.
No Start Condition
GROUND FAULT
Controller shows GROUND FAULT or GFI TRIP; generator may shut down or open breaker.
Ground Fault on Output Circuit
HIGH COOLANT TEMP
Liquid-cooled Guardian standby generator shuts down during run with HIGH COOLANT TEMP or HIGH ENGINE TEMP alarm.
Engine Overheating – Coolant System Fault
HIGH OIL TEMP
Air-cooled Guardian generator shuts down with HIGH OIL TEMP or HIGH ENGINE TEMP alarm after running under load.
Engine Overheating – Air-Cooled System
INTAKE AIR TEMP HIGH
Controller shows INTAKE AIR TEMP HIGH; generator may derate or shut down in hot weather.
High Intake Air Temperature Alarm
LOW BATTERY
Controller displays LOW BATTERY or BATTERY LOW; generator may crank slowly or fail to crank.
Battery Voltage Below Threshold
LOW COOLANT LEVEL
Liquid-cooled Guardian generator displays LOW COOLANT LEVEL or COOLANT LOW and may not start.
Coolant Level Sensor Alarm
LOW FUEL PRESSURE
Generator starts to crank but stalls or runs rough, then shuts down with LOW FUEL PRESSURE or FUEL SUPPLY error.
Insufficient Fuel Supply Pressure
LOW OIL PRESSURE
Generator starts then quickly shuts down with LOW OIL PRESSURE alarm; may not crank again until reset.
Low Oil Pressure Shutdown
MAINTENANCE DUE
Controller displays MAINTENANCE DUE, SERVICE DUE, or similar reminder; generator still runs but service is overdue.
Scheduled Maintenance Interval Reached
OVERCRANK
Generator attempts to start multiple times but fails to run, then shuts down with OVERCRANK message on controller.
Failure to Start – Overcrank Lockout
OVERCURRENT
Generator shuts down with OVERCURRENT or OVERLOAD alarm; may trip internal breaker when large loads start.
Excessive Load or Short Circuit on Output
OVERSPEED
Generator starts but quickly shuts down with OVERSPEED alarm; engine may rev unusually high just before shutdown.
Engine Overspeed Protection Trip
OVERVOLTAGE
Controller shows OVERVOLTAGE; output voltage measures significantly above nominal (e.g., above 130 V line-to-neutral on a 120 V system).
Generator Output Voltage Too High
PHASE LOSS
On three-phase Guardian units, controller displays PHASE LOSS or PHASE FAILURE; generator may shut down or lock out.
Loss of One or More Output Phases
RPM SENSE LOSS
Generator cranks and may briefly fire, then shuts down with RPM SENSE LOSS or similar message.
Engine Speed Signal Loss
SENSOR FAILURE
Controller displays SENSOR FAILURE or GENERIC SENSOR FAULT; may prevent start or cause shutdown.
Analog Sensor Input Fault
SPARK PLUG
Controller maintenance menu indicates SPARK PLUG SERVICE; engine may misfire or start hard.
Spark Plug Wear / Maintenance Reminder
SYNC LOSS
On units with advanced controllers, SYNC LOSS or OUT OF SYNC alarm appears when transferring load.
Loss of Synchronization Between Generator and Utility
UNDERFREQUENCY
Generator runs but controller displays UNDERFREQUENCY or LOW HZ; connected loads may experience dimming lights or sluggish motors.
Engine Running Below Rated Speed
UNDERVOLTAGE
Controller displays UNDERVOLTAGE; output voltage is significantly below nominal even with light load.
Generator Output Voltage Too Low
Symptom
Controller buttons are unresponsive or stick; difficult to change modes or settings.
Keypad / Button Failure
Symptom
Controller display is blank or unreadable; generator will not respond to commands.
Controller Power / Display Failure
Symptom
Excessive blue or white smoke from exhaust during startup and running.
Oil Burning / Incomplete Combustion
Symptom
Excessive exhaust noise or rattling from muffler area; exhaust leak visible as soot around joints.
Exhaust System Leak / Muffler Failure
Symptom
Excessive vibration of generator enclosure and base during operation; may cause noise in nearby structure.
Abnormal Vibration
Symptom
Frequent nuisance tripping of generator main breaker at moderate loads.
Breaker Nuisance Trip
Symptom
Generator continues to run after utility power has been restored; transfer switch may or may not retransfer.
Failure to Return to Standby
Symptom
Generator cranks slowly or not at all; clicking noise from starter area but engine does not turn over.
Hard Cranking / No Crank
Symptom
Generator enclosure or base shows signs of oil leakage onto pad or ground.
Engine Oil Leak
Symptom
Generator fails to automatically start when utility power is lost, but will start manually from the controller.
No Automatic Start on Power Failure
Symptom
Generator runs but produces no AC power at the house; lights and appliances remain off even though engine is running.
No Output Power – Transfer or Breaker Issue
Symptom
Generator runs rough, surges, or misfires under load; lights flicker and engine speed fluctuates.
Engine Misfire / Hunting Under Load
Symptom
Generator starts and stops repeatedly without transferring load; short run cycles followed by shutdown with no clear code.
Short Cycling / Nuisance Shutdown
Symptom
Generator starts automatically on power loss but transfer switch does not move to generator position; house remains on utility or dark.
Transfer Switch Fails to Transfer
Symptom
Strong raw fuel or gas odor around generator during or after operation.
Fuel Odor / Possible Leak
Symptom
Unusual loud knocking, clanking, or metallic noise from engine during operation.
Internal Engine Mechanical Noise
Symptom
Water or moisture accumulation inside generator enclosure; signs of rust or corrosion on components.
Moisture Intrusion / Corrosion
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| AIR FILTER |
Controller shows AIR FILTER or MAINTENANCE AIR FILTER; generator may run rich or lack power.
|
Restricted Air Intake – Maintenance Reminder | View Details |
| CHARGER FAIL |
Controller shows CHARGER FAIL or BATTERY CHARGER FAULT; battery may not stay charged between exercises.
|
Integrated Battery Charger Failure | View Details |
| EMERGENCY STOP |
Controller displays EMERGENCY STOP or E-STOP ACTIVE; generator will not start until cleared.
|
Emergency Stop Circuit Activated | View Details |
| ESTOP ACTIVE |
Display shows ESTOP ACTIVE or REMOTE STOP; generator remains locked out.
|
Remote Emergency Stop or Shutdown Input Active | View Details |
| EXERCISE NOT RUN |
Controller indicates EXERCISE NOT RUN or MISSED EXERCISE; generator has not performed its scheduled weekly test.
|
Missed Automatic Exercise Cycle | View Details |
| FUEL LEAK DETECTED |
Controller or external sensor indicates FUEL LEAK or FUEL ALARM; fuel odor may be present near generator.
|
Fuel Leak Detection Alarm | View Details |
| GENERATOR FAILURE TO START |
Controller logs FAILURE TO START or similar; unit never fires, only cranks or clicks.
|
No Start Condition | View Details |
| GROUND FAULT |
Controller shows GROUND FAULT or GFI TRIP; generator may shut down or open breaker.
|
Ground Fault on Output Circuit | View Details |
| HIGH COOLANT TEMP |
Liquid-cooled Guardian standby generator shuts down during run with HIGH COOLANT TEMP or HIGH ENGINE TEMP alarm.
|
Engine Overheating – Coolant System Fault | View Details |
| HIGH OIL TEMP |
Air-cooled Guardian generator shuts down with HIGH OIL TEMP or HIGH ENGINE TEMP alarm after running under load.
|
Engine Overheating – Air-Cooled System | View Details |
| INTAKE AIR TEMP HIGH |
Controller shows INTAKE AIR TEMP HIGH; generator may derate or shut down in hot weather.
|
High Intake Air Temperature Alarm | View Details |
| LOW BATTERY |
Controller displays LOW BATTERY or BATTERY LOW; generator may crank slowly or fail to crank.
|
Battery Voltage Below Threshold | View Details |
| LOW COOLANT LEVEL |
Liquid-cooled Guardian generator displays LOW COOLANT LEVEL or COOLANT LOW and may not start.
|
Coolant Level Sensor Alarm | View Details |
| LOW FUEL PRESSURE |
Generator starts to crank but stalls or runs rough, then shuts down with LOW FUEL PRESSURE or FUEL SUPPLY error.
|
Insufficient Fuel Supply Pressure | View Details |
| LOW OIL PRESSURE |
Generator starts then quickly shuts down with LOW OIL PRESSURE alarm; may not crank again until reset.
|
Low Oil Pressure Shutdown | View Details |
| MAINTENANCE DUE |
Controller displays MAINTENANCE DUE, SERVICE DUE, or similar reminder; generator still runs but service is overdue.
|
Scheduled Maintenance Interval Reached | View Details |
| OVERCRANK |
Generator attempts to start multiple times but fails to run, then shuts down with OVERCRANK message on controller.
|
Failure to Start – Overcrank Lockout | View Details |
| OVERCURRENT |
Generator shuts down with OVERCURRENT or OVERLOAD alarm; may trip internal breaker when large loads start.
|
Excessive Load or Short Circuit on Output | View Details |
| OVERSPEED |
Generator starts but quickly shuts down with OVERSPEED alarm; engine may rev unusually high just before shutdown.
|
Engine Overspeed Protection Trip | View Details |
| OVERVOLTAGE |
Controller shows OVERVOLTAGE; output voltage measures significantly above nominal (e.g., above 130 V line-to-neutral on a 120 V system).
|
Generator Output Voltage Too High | View Details |
| PHASE LOSS |
On three-phase Guardian units, controller displays PHASE LOSS or PHASE FAILURE; generator may shut down or lock out.
|
Loss of One or More Output Phases | View Details |
| RPM SENSE LOSS |
Generator cranks and may briefly fire, then shuts down with RPM SENSE LOSS or similar message.
|
Engine Speed Signal Loss | View Details |
| SENSOR FAILURE |
Controller displays SENSOR FAILURE or GENERIC SENSOR FAULT; may prevent start or cause shutdown.
|
Analog Sensor Input Fault | View Details |
| SPARK PLUG |
Controller maintenance menu indicates SPARK PLUG SERVICE; engine may misfire or start hard.
|
Spark Plug Wear / Maintenance Reminder | View Details |
| SYNC LOSS |
On units with advanced controllers, SYNC LOSS or OUT OF SYNC alarm appears when transferring load.
|
Loss of Synchronization Between Generator and Utility | View Details |
| UNDERFREQUENCY |
Generator runs but controller displays UNDERFREQUENCY or LOW HZ; connected loads may experience dimming lights or sluggish motors.
|
Engine Running Below Rated Speed | View Details |
| UNDERVOLTAGE |
Controller displays UNDERVOLTAGE; output voltage is significantly below nominal even with light load.
|
Generator Output Voltage Too Low | View Details |
| – |
Controller buttons are unresponsive or stick; difficult to change modes or settings.
|
Keypad / Button Failure | View Details |
| – |
Controller display is blank or unreadable; generator will not respond to commands.
|
Controller Power / Display Failure | View Details |
| – |
Excessive blue or white smoke from exhaust during startup and running.
|
Oil Burning / Incomplete Combustion | View Details |
| – |
Excessive exhaust noise or rattling from muffler area; exhaust leak visible as soot around joints.
|
Exhaust System Leak / Muffler Failure | View Details |
| – |
Excessive vibration of generator enclosure and base during operation; may cause noise in nearby structure.
|
Abnormal Vibration | View Details |
| – |
Frequent nuisance tripping of generator main breaker at moderate loads.
|
Breaker Nuisance Trip | View Details |
| – |
Generator continues to run after utility power has been restored; transfer switch may or may not retransfer.
|
Failure to Return to Standby | View Details |
| – |
Generator cranks slowly or not at all; clicking noise from starter area but engine does not turn over.
|
Hard Cranking / No Crank | View Details |
| – |
Generator enclosure or base shows signs of oil leakage onto pad or ground.
|
Engine Oil Leak | View Details |
| – |
Generator fails to automatically start when utility power is lost, but will start manually from the controller.
|
No Automatic Start on Power Failure | View Details |
| – |
Generator runs but produces no AC power at the house; lights and appliances remain off even though engine is running.
|
No Output Power – Transfer or Breaker Issue | View Details |
| – |
Generator runs rough, surges, or misfires under load; lights flicker and engine speed fluctuates.
|
Engine Misfire / Hunting Under Load | View Details |
| – |
Generator starts and stops repeatedly without transferring load; short run cycles followed by shutdown with no clear code.
|
Short Cycling / Nuisance Shutdown | View Details |
| – |
Generator starts automatically on power loss but transfer switch does not move to generator position; house remains on utility or dark.
|
Transfer Switch Fails to Transfer | View Details |
| – |
Strong raw fuel or gas odor around generator during or after operation.
|
Fuel Odor / Possible Leak | View Details |
| – |
Unusual loud knocking, clanking, or metallic noise from engine during operation.
|
Internal Engine Mechanical Noise | View Details |
| – |
Water or moisture accumulation inside generator enclosure; signs of rust or corrosion on components.
|
Moisture Intrusion / Corrosion | View Details |
No matching codes found
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