Takagi Code 111: Ignition Failure

The Short Answer: Takagi 111 (and two-digit 11) is ignition failure: three tries, no proven flame, lockout. Gas cock closed, lazy spark, dirty flame rod, tripped hi-limit, or a dead overheat fuse — not a full code chart. Photograph it. Fix the obvious cause. Reset once. Do not measure gas pressure yourself. Do not keep cycling a flooded burner.

Search Intent & The Real Problem

The remote or the PCB LED says 111. The shower died. This is not the whole Takagi problem list. 111 is the three-digit ignition code on T-H3 / T-D2 / T-M32 / T-M50 and many AO Smith-badged twins. Older T-KJr2 / T-K4 remotes often show 11 for the same fault. 121 (or 12) is different: it lit, then lost flame. Do not treat a 13 remaining-flame or a 14/16 overheat as 111.

What other guides get wrong

They paste the entire 10/11/12/14/16 table into a 111 article. They tell you to reset until it fires. Ten resets glaze the igniter. They send homeowners at a manometer. They confuse 111 (never lit) with 121 (lit, then died) and with a packed inlet screen that never calls for fire. And they skip the white hi-limit button, so you chase spark on a limit that is open.

Step-by-Step Troubleshooting

Step 1: Photograph 111 vs 11 vs 121 — then stop guessing

• What to look for: Two-digit vs three-digit on your remote or 7-seg LED. Model on the rating plate (T-KJr2, T-K4, T-H3, T-D2, T-M-series, AO Smith ATI/GTS twins).
• Required tools: Phone photo of the code before you kill power. Reset procedure is last, not first.

Step 2: Gas cock, other appliances, LP — no manometer

• What to look for: Appliance shutoff handle parallel to the pipe (open). Other gas appliances lighting. LP bottles not empty; a cold first-stage regulator frosting on a 20°F morning will 111 a tankless that was fine in July. 1/2” flex on a 140–199 kBTU Takagi is a starvation install — it lights the stove and will not light this. New install or a meter relight in the last day can be air in the line. That is a licensed purge and leak test, not a union crack.
• Required tools: Eyes on the cock and the flex. No fittings wrenches.

Manifold and inlet pressure are licensed (Takagi plates vary — often on the order of 3.5–10.5 in. w.c. natural gas depending on model, LP higher — confirm the rating plate, never by ear).

Step 3: Spark at the igniter — one look through the sight glass

• What to look for: Cover on. One hot-water call. Blue-white snap at the electrode through the sight glass, then gas, then flame. No spark = igniter, high-voltage lead, PCB fuse. Spark, no flame = gas path (step 2) or a burner full of dust/spider silk on an outdoor unit. Brief flame, then 111 = flame rod did not prove (step 4). A bang is delayed ignition — shut it down, not a second trial.
• Required tools: Ears and eyes. One trial. Do not run it with the cover off “to see better.”

Repeated 111 cycles after you already saw spark are how igniters glaze. Stop.

Step 4: Flame rod, hi-limit, OHCF — safeties that fake a dead igniter

• What to look for: Flame rod sooted so the board never sees ionization (often a few microamps when healthy — a licensed reading). White hi-limit button on many T-H3-class cabinets: power off, press until it clicks. If it trips again, that is overheat or a failed limit — not another 111 reset. OHCF (overheat cutoff fuse) is a one-shot thermal fuse around the exchanger; open fuse = no ignition, licensed replacement after you find why it opened. PCB glass fuse blown after a wet leak — cabinet leak first.
• Required tools: Power off before you touch the hi-limit. No sandpaper-as-a-lifestyle on the rod; a light wipe on a cool rod is the most a homeowner should do. Do not bend the gap into a pretzel. Do not jumper the OHCF.

A 111 with a flame you can see is almost never “no gas.” It is sense, wiring, or the board.

Step 5: One reset after the cause — then hire it

• What to look for: Cause addressed (cock open, filter not relevant to 111 unless the unit never tries, vent not a 10). Power off 10–30 seconds, on. Unit fires in the trial window, stable flame, no bang, no 111 return. Same 111 on the next shower is the end of DIY. Inlet screen grit causes no-fire without a 111 more often than it causes 111; do not descale a 111 as step one.
• Required tools: Your hand on the switch. No paperclip in the PCB.

When DIY Ends: Calling a Licensed Pro

Stop at gas odor, delayed-ignition bangs, a 13, a hi-limit that will not stay reset, an open OHCF, a wet board, and any gas-pressure or gas-valve work. You may photograph the code, confirm the shutoff, look for spark through the glass, press the hi-limit once with power off, and power-cycle once. Combustion, manometer, igniter/flame-rod replacement inside the burner, and PCB work are licensed. Takagi / AO Smith will not smile on an igniter you reset through a flooded burner all weekend.

Frequently Asked Questions

Q: What does Takagi code 111 mean? A: Ignition failure after three unsuccessful tries. The board did not prove flame. 11 is the same fault on many two-digit remotes. 121/12 is flame loss after a successful light.

Q: How do I clear a Takagi 111? A: Photograph the code, fix the obvious cause (gas cock, LP, one spark look), then power off 10–30 seconds. One reset. A 111 that returns is a licensed diagnosis, not a reset schedule.

Q: Can I check gas pressure on a Takagi 111 myself? A: No. Confirm the shutoff and that other appliances light. Inlet and manifold pressure are a licensed manometer job. Do not loosen fittings to “bleed air.”