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.
96 fault codes documented· 5 brands (Onan, Generac, Kohler, Perkins, Kubota) · RV / standby / industrial
Most Common Generator Fault Codes
Showing 30 of 96 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
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
High Engine Coolant Temperature Shutdown (1 Blink)
ONAN-2 critical
Low Oil Pressure Fault (2 Blinks)
ONAN-29 critical
Low Coolant Level Shutdown Detected
PERKINS-100-1 critical
Engine Oil Pressure Low (Most Severe)
PERKINS-110-0 critical
Engine Coolant Temperature High (Most Severe)
PERKINS-111-1 critical
Engine Coolant Level Low
PERKINS-1239-31 critical
Common-Rail Fuel Leak Detected, ECM Derate or Shutdown
PERKINS-190-0 critical
Engine Overspeed: Engine Speed Above Limit (Most Severe)
GENERAC-1100 serious
Overcrank: Engine Cranks but Will Not Start
GENERAC-1116 serious
RPM Sense Signal Lost Due to Wiring Fault
GENERAC-1200 serious
Overspeed: Controller Detected High Engine RPM
GENERAC-1501 serious
RPM Sensor Loss: No Valid Engine Speed Signal (Generac 1500-1522 Family)
GENERAC-1502 serious
RPM Sensor Loss: No Valid Engine Speed Signal (Generac 1500-1522 Family)
GENERAC-1505 serious
RPM Sensor Loss: No Valid Engine Speed Signal (Generac 1500-1522 Family)
GENERAC-1517 serious
RPM Sensor Loss: No Valid Engine Speed Signal (Generac 1500-1522 Family)
GENERAC-1518 serious
RPM Sensor Loss: No Valid Engine Speed Signal (Generac 1500-1522 Family)
GENERAC-1521 serious
RPM Sensor Loss: No Valid Engine Speed Signal (Generac 1500-1522 Family)
GENERAC-1522 serious
RPM Sensor Loss: No Valid Engine Speed Signal (Generac 1500-1522 Family)
GENERAC-1600 serious
Underspeed: Engine RPM Too Slow
GENERAC-1601 serious
Underspeed: Engine RPM Too Slow (Generac 1600-1603 Family)
GENERAC-1750 serious
Wiring Harness Fault Detected During Pre-Start
GENERAC-1751 serious
Wiring Loop Continuity Fault Detected
GENERAC-1752 serious
Internal Controller Communication Bus Failure
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