Takagi Error Code 11: Ignition Failure on the 110 (T-KJr2) and 310 (T-K4)

What the code means

Takagi's troubleshooting guide for the 110 (T-KJr2), 310 (T-K4) and 510 (T-D2) lists code 11 as Ignition Failure: the heater does not fire after three failed attempts at ignition. On the 110 and 310 the remote controller shows 11 and the red LED on the computer board flashes three times. The 510 and the newer models show the same problem as code 111. Code 12 is the related flame loss code, where the flame went out while the heater was still supposed to be running; it also shows as three flashes on the 110 and 310, so if you only have the red light to go by, a remote controller tells you which of the two you have.

Likely causes

• A tripped hi-limit switch
• Not enough gas reaching the heater, or debris or air in the gas line
• A faulty pressure regulator at the gas meter
• On propane units, a cold regulator during colder parts of the day
• Gas supply pressure out of spec in standby or while the heater runs
• A disconnected clear plastic tube between the proportional gas valve and the combustion chamber
• A blown overheat cutoff fuse (OHCF)
• A dirty flame sensor (the flame comes on for only 1 to 2 seconds, then goes out)
• A weak or missing igniter spark from loose igniter wires or a failed igniter
• A blocked vent (bird nests, animals, trash), or a computer board or gas solenoid fault

Safe DIY checks

1. Reset the hi-limit switch: turn the power to the heater off, push the white button in until you hear and feel it click, then turn the power back on and test. If the heater fires, Takagi says the cause of the trip still has to be found, so call its Technical Service Department or a technician.
2. Make sure the gas valve to the heater is fully open and, on propane, that the tank isn't empty. If you smell gas, leave the house and call your gas company from outside.
3. If the heater was just installed or the gas was recently off, air in the gas line is a common cause; Takagi's guide covers purging it, and a technician can do it quickly if you're not comfortable working on gas fittings.
4. Check the outdoor vent termination for bird nests, animals, trash, snow or ice.
5. Watch through the sight glass next to the igniter while the heater tries to light. Takagi says a strong blue spark stays steady and in place, while a weak spark jumps around. Note what you see for the technician.
6. If the flame comes on for only 1 to 2 seconds before going out, the flame sensor likely needs cleaning, which Takagi's guide covers as part of cleaning the burner and rod assembly.

Parts that commonly fix it

Always match the part number to your exact model.

Related codes

• 101 Takagi Tankless Water Heater 101
• 111 Takagi Tankless Water Heater 111
• 121 Takagi Tankless Water Heater 121
• 291 Takagi Tankless Water Heater 291
• 391 Takagi Tankless Water Heater 391

All Takagi codes →

Sources

1. Takagi Troubleshooting Guide 321923-000 for 110 (T-KJr2), 310 (T-K4) and 510 (T-D2): Table 2 error codes (11 on the 110/310 remote, three red LED flashes, 111 on the 510, Ignition Failure; 12 Flame Loss also three flashes); Error Code 111 / Three Flashes / 11 checklist (hi-limit reset, gas supply and air or debris, meter regulator, cold propane regulator, supply pressure in standby and running, clear plastic tube, OHCF, flame sensor cleaning, spark through sight glass, igniter wires, vent blockages, PC board or gas solenoid fault); gas pressure check and gas line purge procedures
2. Takagi On-Demand Water Heater Service Handbook for 240, 340 & 540 Condensing Models (2000534342): code 111 for the same ignition failure on newer condensing models