Fault 57

Onan Generator: “Fault 57”

info RV generator fault codes

Safety Extended priming can flood the engine and push raw fuel through the system. This is a fuel-burning engine. Never run it in an enclosed space or occupy the vehicle while it runs without a working carbon monoxide detector, and let hot parts cool before touching anything.

What it means

Overprime. A control switch — the one on the genset or the remote one inside the vehicle — was held in the Prime position for more than three minutes. This is the controller protecting the fuel system, not a defect in the generator.

Most likely causes

  1. Something physically holding the local or remote switch in Prime — a jammed rocker, trapped trim, an object leaning on the panel most likely
  2. A remote switch that sticks instead of springing back common
  3. Priming deliberately held far too long while chasing a hard start common

Safe checks you can do yourself

How to reset / clear Fault 57

  1. Release the switch, then prime in short bursts rather than one long hold.
  2. To re-display a logged code, press Stop three times within five seconds — the blinking times out after five minutes (fifteen on the HGJAA series). The controller keeps replaying the last fault even after the cause is gone; only a successful run clears it.

When to call a technician

The code returns with both switches confirmed free — the switch or its wiring is shorted.

Accuracy notes

Two switches can cause this and people only check one. The remote panel inside the coach is the one usually overlooked, because nobody is standing at it when the fault appears.

Applies to

Onan Quiet Diesel HDKCA / HDKCB

FAQ

What does Onan Generator code "Fault 57" mean?

Overprime. A control switch — the one on the genset or the remote one inside the vehicle — was held in the Prime position for more than three minutes. This is the controller protecting the fuel system, not a defect in the generator.

How do I reset Onan Generator Fault 57?

Release the switch, then prime in short bursts rather than one long hold. To re-display a logged code, press Stop three times within five seconds — the blinking times out after five minutes (fifteen on the HGJAA series). The controller keeps replaying the last fault even after the cause is gone; only a successful run clears it.

What is the most common cause of Fault 57 on a Onan Generator?

The most likely cause is something physically holding the local or remote switch in prime — a jammed rocker, trapped trim, an object leaning on the panel.

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Sources

● Checked against 1 manufacturer document · 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