Onan Generator: “Fault 31”
danger RV generator fault codes
What it means
Overspeed fault. The engine speed exceeded 3400 rpm, so the controller shut the generator down to protect it. Read as three blinks, a pause, then one blink.
Most likely causes
- Governor or governor-actuator malfunction allowing engine to run away common
- Controller / speed-sensing fault common
- Throttle/linkage or fuel system fault driving speed too high less common
Safe checks you can do yourself
- Note the conditions when it tripped, but do not attempt to defeat or readjust the governor yourself.
- Confirm the code by reading the blink pattern (3 then 1) to be sure it is overspeed (31) and not engine-stopped (36).
How to reset / clear Fault 31
- The official corrective action is to see an authorized Onan dealer - overspeed is not a homeowner adjustment.
- To re-read the logged code, press Stop three times within 5 seconds (the code stops blinking after about 5 minutes).
When to call a technician
Always for overspeed - the manufacturer directs you to an authorized Onan/Cummins dealer rather than DIY repair.
Accuracy notes
Overspeed is the true meaning of 31, and it is frequently confused with 36. Worth knowing where it applies: code 31 appears in Onan troubleshooting tables for other series, but it is in neither the KY (Spec J–N) operator manual nor the HDKCA/HDKCB Quiet Diesel manual. Check the table for your own model and spec letter before acting on it.
Applies to
Onan RV QG / KY series RV gensets · Onan blink-code-controller RV gensets (HGJAA/HGJAB-class)
FAQ
What does Onan Generator code "Fault 31" mean?
Overspeed fault. The engine speed exceeded 3400 rpm, so the controller shut the generator down to protect it. Read as three blinks, a pause, then one blink.
How do I reset Onan Generator Fault 31?
The official corrective action is to see an authorized Onan dealer - overspeed is not a homeowner adjustment. To re-read the logged code, press Stop three times within 5 seconds (the code stops blinking after about 5 minutes).
What is the most common cause of Fault 31 on a Onan Generator?
The most likely cause is governor or governor-actuator malfunction allowing engine to run away.
Related · Onan generator
Engine Stopped fault. The engine stopped on its own without the… Fault 14
Overfrequency fault. The engine governor could not hold the rated output… Fault 19
Governor actuator fault. The controller detected an open or shorted…
Sources
- Onan RV Generator Troubleshooting Codes (Table 5) — TABLE 5 - OVERSPEED FAULT-CODE NO. 31 (Engine speed greater than 3400 rpm) (Cummins/Onan (hosted by Heartland Owners))
- Operator Manual — RV Generator Set KY (Spec J–N) — 981-0159 (Issue 9), Section 4 Troubleshooting, Table 2 (Cummins Inc. (Onan))
- Operator Manual — RV Generator Set HDKCA / HDKCB (Spec A–E) — 0981-0173 (Issue 10), Section 4 Troubleshooting, Table 4-1 (Cummins Inc. (Onan Quiet Diesel))
● Checked against 3 manufacturer documents · Last verified 2026-08-07 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual. How we verify