Kohler generator code EngineSpeed High
High severity — Engine speed exceeded roughly 115% of normal running speed for more than 0.3 seconds — an overspeed condition — and the controller shut the engine down immediately.
Applies to: Kohler residential standby generators with an RDC2 or DC2 controller
What it means
An overspeeding engine doesn't sound subtle — it revs noticeably higher and often sounds like it's straining or racing right before the controller cuts it off. That reaction is deliberately fast: RDC2 and DC2 controllers watch engine speed continuously, and the instant it climbs past roughly 115% of normal running speed for more than three-tenths of a second, the engine shuts down immediately. There's no grace period here the way there is with some slower-tripping faults, because a genuinely overspeeding engine can throw a rod, damage the alternator windings, or in rare cases keep accelerating in a way that becomes an outright physical hazard.
Most common causes
Overspeed almost always traces back to something in the throttle or governor path:
- Governor or electronic speed control malfunction
- Throttle linkage binding or disconnected
- Fuel mixture issue causing unstable governing
What you can check yourself
What's reasonable to look at from a safe distance:
- Visually inspect the throttle linkage for anything loose, binding, or disconnected
- Clear the fault and, from a safe distance, watch whether the engine races or surges on the next attempt
If you see or hear the engine actually racing on a restart attempt, don't keep cycling the controller hoping it clears itself — shut it down at the main disconnect and stop there rather than watching it happen a second time.
All codes for this brand
Every Kohler generator fault code — full list with what differs between models.
Related codes: EngineSpeed Low and Voltage High. See the Overspeed Shutdown symptom page for the broader picture.