Takagi error codes
23 codes that Takagi publishes for a tankless water heater, each quoted from the maker’s own manual or support page and explained on its appliance’s page. Pick the appliance, or type the code from the display: only Takagi codes are searched here.
If you smell gas
Stop: do not reset, relight or check anything on this page. Takagi’s own words, from the Owner’s Guide operating label, page 42, under “What to do if you smell gas”:
- Do not try to light any appliance.
- Do not touch any electric switch; do not use any phone in your building.
- Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instructions.
- If you cannot reach your gas supplier, call the fire department.
Calling from a neighbor’s phone means leaving the building first. Source: On-Demand Water Heater Installation Manual and Owner’s Guide, 240 (T-H3J), 340 (T-H3S), 540 (T-H3) (68A161-2), Error codes, pages 52–54
Every Takagi appliance we cover
| Appliance | Codes | Source |
|---|---|---|
| Takagi tankless water heater | 23 codes | Takagi, 2 documents |
Takagi tankless water heater error codes
23 codes from Takagi. 16 of them are marked for a licensed professional; for the rest the page gives the checks the maker lets an owner do. Tap a code for its meaning:
Tankless gas water heater: do only the owner checks its manual gives for that code — open the gas and water shut-off valves, check a propane tank has gas, clean a filter the way the manual shows you, clear snow or debris from the vent ends outside, turn it off and on at the controller. Leave gas pressure, the burner, the gas valve, wiring and circuit boards alone. Everything else is for a licensed professional — in the manuals’ words, a qualified installer, service agency or the gas supplier. If you smell gas, do none of the checks: follow the maker’s gas-smell instructions at the top of the page. Two Takagi models can use different codes: your model’s manual is the authority.
Sources
Every Takagi code on this site comes from these pages, published by Takagi and read on the date shown.
- Takagi (tankless water heater): On-Demand Water Heater Installation Manual and Owner’s Guide, 240 (T-H3J), 340 (T-H3S), 540 (T-H3) (68A161-2), Error codes, pages 52–54 Checked 2026-09-29.
- Takagi (tankless water heater): Non-Condensing Models Troubleshooting Guide, 110 (T-KJr2), 310 (T-K4), 510 (T-D2) (321923), table 2 Error Codes Checked 2026-09-29.