Generator Fault Codes
Standby and portable generators -- Onan, Generac, Kohler, Perkins. Whether it's a Cummins-Onan in an RV, a Generac Guardian doing whole-house standby, or a Perkins-powered prime-power genset on a job site, the fault codes follow predictable patterns: low oil pressure shutdowns, overcrank failures, high engine temp, and overspeed / underspeed governor faults are the universal flavors. Most can be diagnosed and cleared from the operator panel; deeper SPN/FMI requires the brand's dealer software.
112 fault codes documented· 5 brands (Onan, Generac, Kohler, Perkins, Kubota) · RV / standby / industrial
Most Common Generator Fault Codes
Showing 30 of 112 Generators codes across Onan, Generac, Kohler, Perkins, and Kubota, sorted by severity. Each links to causes, diagnostics, common fixes, and repair cost estimates.
GENERAC-1300 critical
Low Oil Pressure Shutdown Detected
GENERAC-1502 critical
Engine Overspeed Shutdown Detected
GENERAC-1600 critical
High Engine Temperature Shutdown Detected
GENERAC-1601 critical
High Cylinder Head Temperature Shutdown
GENERAC-2099 critical
Alternator Rotor Excitation Failure, No AC Output
KOHLER-17 critical
Low Oil Pressure Shutdown During Engine Run
KOHLER-18 critical
High Engine Temperature Shutdown Triggered
KOHLER-19 critical
Engine Overspeed Shutdown Detected
KOHLER-COMMAND-BLINK-2 critical
Low Oil Pressure Shutdown Detected
KOHLER-COMMAND-BLINK-3 critical
Cylinder Head Overheat Shutdown Detected
KUBOTAGEN-E02 critical
Engine Overspeed Shutdown RPM Limit Exceeded
KUBOTAGEN-E03 critical
Low Engine Oil Pressure Shutdown Detected
KUBOTAGEN-E04 critical
High Engine Coolant Temperature Shutdown
KUBOTAGEN-E05 critical
Low Coolant Level Detected, Run Blocked
ONAN-1 critical
Low Oil Pressure Shutdown: Engine Protected
ONAN-2 critical
High Engine Temperature Shutdown Triggered
ONAN-29 critical
Low Coolant Level Shutdown Detected
ONAN-3 critical
Engine Overspeed Shutdown Detected
PERKINS-100-1 critical
Low Engine Oil Pressure Shutdown Detected
PERKINS-110-0 critical
High Coolant Temperature Emergency Shutdown
PERKINS-111-1 critical
Low Coolant Level Shutdown Triggered
PERKINS-1239-31 critical
Common-Rail Fuel Leak Detected, ECM Derate or Shutdown
PERKINS-190-0 critical
Engine Overspeed Shutdown: RPM Exceeded Safe Limit
GENERAC-1100 serious
Low Battery Voltage Detected on Controller
GENERAC-1116 serious
RPM Sense Signal Lost Due to Wiring Fault
GENERAC-1200 serious
Stepper Motor Underspeed During Start or Load
GENERAC-1501 serious
Engine RPM Dropped Below Operating Threshold
GENERAC-1505 serious
Engine RPM Signal Lost During Operation
GENERAC-1521 serious
Output Frequency Dropped Below Acceptable Range
GENERAC-1522 serious
Output Frequency Too High, Possible Overspeed or Governor Fault
Generator Brands
| Brand | Applications | Notes |
|---|---|---|
| Onan (Cummins) | RV gensets (Microquiet 4000, Microlite 2800/4000, Quiet Diesel 6000/7500/10000) + commercial standby | RV-focused. Two-digit fault codes via the operator panel; use PRIME/STOP to reset. Quiet Diesel models are Kubota-powered. |
| Generac | Home standby (Guardian 7-24kW, PowerPact 7.5kW, Protector 25-48kW) + portable generators | Largest residential standby brand. 4-digit fault codes (1100 Overcrank, 1300 Low Voltage, 1500 Overspeed/Underspeed, etc.) on Nexus and Evolution controllers. |
| Kohler | Residential and commercial standby gensets, marine, industrial | Premium standby brand. Codes via the OnCue Plus app or local controller display. Common variant: KG/KGS-series. |
| Perkins | Industrial and prime-power gensets (FG Wilson and many OEMs) | Caterpillar-owned industrial diesel engine brand. Powers many industrial and prime-power generator sets globally. |
| Kubota Genset | RV gensets (SQ-1100, SQ-3300), mobile (GL-7000/11000), portable (J-series). Powers most Onan Quiet Diesel internals. | Reliable industrial diesels (D902, D1105, V1505) packaged for genset use. Fault codes display as E:01-E:16 on the operator panel. |
Common Generator Issues
- Overcrank (Generac 1100, Onan blink-1) -- typically weak battery or empty LP / fuel tank
- Overspeed / Underspeed (Generac 1500) -- governor linkage stuck or stepper motor failure
- High engine temperature shutdown (Onan 2) -- blocked compartment airflow or low coolant
- Low oil pressure shutdown (Onan 1) -- oil level low or worn pump
- Operator control panel faults (Onan 13) -- moisture corrosion or bad harness
- Genset will not transfer to load -- automatic transfer switch (ATS) wiring or fault
- Fuel system air leak after run-out causing repeated start failures