Takagi tankless water heater error codes
Takagi numbers its faults in three digits — 031 through 991 — and splits its documentation by condensing and non-condensing models, with a separate troubleshooting guide for each. The two ranges do not share a code table, so the first thing to establish is which one is on your wall.
Pick your series below — Takagi code meanings are documented per series, because the same number can point to a different fault on a different generation.
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Condensing
24 documented codes
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Non-Condensing
18 documented codes
Codes documented on more than one Takagi series
Pick a number to see what it means on each series side by side — useful when you know the code but not the generation.
Not sure which series you own? The model-number decoder matches the number on your rating label to the right table.
All Takagi codes in one table
| Code | Series | Error | Verdict |
|---|---|---|---|
| 031 | Condensing | Incorrect DIP switch settings | Call a pro |
| 101 | Condensing | Abnormal combustion (warning) | Call a pro |
| 111 | Condensing | Ignition failure | Call a pro |
| 121 | Condensing | Flame loss | Call a pro |
| 311 | Condensing | Output thermistor fault | Part replacement |
| 321 | Condensing | Inlet thermistor fault | Part replacement |
| 331 | Condensing | Mixing thermistor fault | Part replacement |
| 341 | Condensing | Exhaust thermistor fault | Call a pro |
| 391 | Condensing | Air-fuel ratio rod failure | Call a pro |
| 441 | Condensing | Flow sensor fault | Part replacement |
| 510 | Condensing | Main and solenoid gas valve fault | Call a pro |
| 551 | Condensing | Solenoid valve fault | Call a pro |
| 611 | Condensing | Fan motor fault | Call a pro |
| 621 | Condensing | Exhaust fan motor fault (indoor models) | Call a pro |
| 631 | Condensing | External pump fault | Part replacement |
| 651 | Condensing | Flow adjustment valve fault | Part replacement |
| 661 | Condensing | Water bypass valve fault | Part replacement |
| 701 | Condensing | Proportional valve or computer board fault | Call a pro |
| 711 | Condensing | Hi-limit switch or overheat cutoff fuse | Call a pro |
| 721 | Condensing | False flame detection | Call a pro |
| 741 | Condensing | Remote controller communication failure | Part replacement |
| 761 | Condensing | Easy-Link communication failure | Call a pro |
| 941 | Condensing | Abnormal exhaust temperature | Call a pro |
| 991 | Condensing | Abnormal combustion | Call a pro |
| 031 | Non-Condensing | Incorrect DIP switch settings | Call a pro |
| 55 | Non-Condensing | Abnormal solenoid gas valve (T-K4, T-KJr2) | Call a pro |
| 101 | Non-Condensing | Abnormal combustion (warning) | Call a pro |
| 111 | Non-Condensing | Ignition failure | Call a pro |
| 121 | Non-Condensing | Flame loss | Call a pro |
| 311 | Non-Condensing | Output thermistor fault | Part replacement |
| 321 | Non-Condensing | Inlet thermistor fault | Part replacement |
| 331 | Non-Condensing | Mixing thermistor fault (T-D2) | Part replacement |
| 391 | Non-Condensing | Air-fuel ratio rod failure | Call a pro |
| 441 | Non-Condensing | Flow sensor fault (Easy-Link systems) | Part replacement |
| 510 | Non-Condensing | Abnormal gas valves | Call a pro |
| 611 | Non-Condensing | Fan motor fault | Call a pro |
| 651 | Non-Condensing | Flow adjustment valve fault (Easy-Link systems) | Part replacement |
| 701 | Non-Condensing | Computer board fault | Call a pro |
| 721 | Non-Condensing | False flame detection | Call a pro |
| 741 | Non-Condensing | Remote controller communication failure | Part replacement |
| 761 | Non-Condensing | Easy-Link communication failure | Call a pro |
| 991 | Non-Condensing | Abnormal combustion | Call a pro |
Each code links to a full page: what the manual says for that exact series, the likely fix, and what it should cost.