Rinnai tankless water heater error codes
Rinnai is one of the most widely installed tankless water heater brands in the US. Its diagnostic codes are grouped by series generation — SENSEI RX/CX, SENSEI, and the older non-SENSEI models — and the same two-digit number can point at a different component depending on which generation is on the wall. Every code below is read from Rinnai's own diagnostic documentation for the exact series, not averaged across the brand.
Pick your series below — Rinnai code meanings are documented per series, because the same number can point to a different fault on a different generation.
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SENSEI RX
31 documented codes
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All Rinnai codes in one table
| Code | Series | Error | Verdict |
|---|---|---|---|
| 03 | SENSEI RX | Power interruption during bath fill | DIY fix |
| 10 | SENSEI RX | Air supply or exhaust blocked, or the condensate trap is full | Call a pro |
| 11 | SENSEI RX | No ignition | Call a pro |
| 12 | SENSEI RX | Flame failure | Call a pro |
| 14 | SENSEI RX | Overheat sensor or thermal fuse tripped | Call a pro |
| 15 | SENSEI RX | Venturi control fault | Call a pro |
| 16 | SENSEI RX | Outlet water temperature too high | Call a pro |
| 17 | SENSEI RX | Venturi blockage | Call a pro |
| 18 | SENSEI RX | Gas valve adjustment limit reached | Call a pro |
| 19 | SENSEI RX | Electrical grounding fault | Call a pro |
| 21 | SENSEI RX | Data transfer error | Call a pro |
| 22 | SENSEI RX | Gas valve adjustment fault | Call a pro |
| 25 | SENSEI RX | Condensate pump fault or blocked condensate drain | DIY fix |
| 32 | SENSEI RX | Outgoing water temperature thermistor fault | Part replacement |
| 33 | SENSEI RX | Heat exchanger thermistor fault | Part replacement |
| 34 | SENSEI RX | Lime detecting thermistor fault | Part replacement |
| 38 | SENSEI RX | Exhaust gas temperature sensor fault | Call a pro |
| 41 | SENSEI RX | Freeze protection sensor fault | Part replacement |
| 51 | SENSEI RX | Inlet water temperature thermistor fault | Part replacement |
| 52 | SENSEI RX | Gas valve fault | Call a pro |
| 54 | SENSEI RX | Exhaust gas temperature too high | Call a pro |
| 61 | SENSEI RX | Combustion fan motor fault | Call a pro |
| 63 | SENSEI RX | Recirculation low flow | DIY fix |
| 65 | SENSEI RX | Water flow control valve fault | Part replacement |
| 66 | SENSEI RX | Bypass flow servo fault | Part replacement |
| 70 | SENSEI RX | PC board fault | Call a pro |
| 71 | SENSEI RX | Gas solenoid valve fault | Call a pro |
| 72 | SENSEI RX | Flame rod fault | Call a pro |
| FF | SENSEI RX | Maintenance performed marker | DIY fix |
| LC | SENSEI RX | Scale build-up lockout | DIY fix |
| SS | SENSEI RX | Service soon reminder | DIY fix |
Each code links to a full page: what the manual says for that exact series, the likely fix, and what it should cost.