Generac Generator Fault Codes
What every fault code and warning on a Generac Guardian or Protector standby generator's Evolution or Nexus display actually means — causes, what's safe to check yourself, and when it's time to call a dealer.
How to read your Generac's fault code display
Generac's home standby line has used two generations of digital controller — Evolution and its successor Nexus — and both present faults the same basic way: a small LCD panel that normally shows engine status cycles instead to a message when something trips. Most shutdown faults show up as a 4-digit number, like 1100 or 1400, tied to a specific protective system inside the controller (starting, oil pressure, engine temperature, and so on). A handful of conditions — Low Battery and Charger Warning among them — are worded warnings rather than numbers, because they don't stop the engine and aren't tied to a single numeric fault family.
When a numeric code appears, the unit has already shut itself down or refused to start, and it will sit on that message until someone clears it. On most Evolution and Nexus panels that means turning the AUTO/OFF/MANUAL switch to OFF, waiting a few seconds, then back to AUTO — the display should return to normal standby status if the underlying problem has actually been addressed. If it faults again almost immediately, that's a strong signal the cause wasn't fixed, not that the reset didn't "take." Many panels also keep an alarm history you can scroll into from the menu, which is worth checking if a fault cleared before you saw exactly what number it showed.
All Generac fault codes
| Code | What it means | Severity |
|---|---|---|
| 1100 | Engine cranked through its full attempt sequence without starting (Overcrank) | High |
| 1200 | Engine speed exceeded the safe governed limit (Overspeed) | High |
| 1300 | Oil pressure switch reported pressure below the safe threshold | High |
| 1400 | Engine temperature exceeded its safe operating limit | High |
| 1501 / 1505 / 1511 / 1515 | Controller lost the RPM/timing signal confirming the engine is turning | High |
| 1800 | Output voltage climbed too high, usually a voltage-regulator fault | High |
| 1900 | Output voltage fell below about 80% of rated voltage for 10+ seconds | Medium |
| 2100 | Current draw exceeded what the unit is rated to supply (Overload) | Medium |
| Low Battery | Starting-battery voltage measured below about 12.1V for 60+ seconds (warning, not a shutdown) | Medium |
| Charger Warning | Built-in charger still hadn't brought the battery above ~12.5V after an 18-hour charge cycle | Low |
Start with the symptom instead
Not sure which code is on your display, or working from a blank panel? These cover the same ground from the generator's behavior rather than its exact wording:
- Generator Won't Start
- Generator Runs Then Shuts Down
- Overspeed Shutdown
- Low Battery or Charger Fault
- Low Oil Pressure Shutdown
- Overload or Nuisance Tripping
- These run on LP or natural gas and produce mains-voltage output — fuel-line work, the transfer switch, and anything inside the alternator housing should be done or verified by someone licensed to do it.
- Never run or work on a generator inside a garage or other enclosed space; exhaust carbon monoxide is fatal and has no smell.
- If a fault involves a fuel smell during cranking, or scorched/loose output wiring, stop and call a technician rather than repeatedly resetting and restarting.
Not seeing the code you're looking at? Try the site-wide code lookup, or check the Kohler and Briggs & Stratton lists — the same wording can mean something different depending on which controller you actually have.