Takagi Error Codes and
Troubleshooting Guide

Takagi error codes for easy troubleshooting tankless water heaters. How to use the diagnostic system to repair the faulty Takagi heater. Find the most frequent error codes and recommendations for an easy fix. If you need help, contact professionals.

Takagi tankless water heaters are equipped with an advanced computer board and self-diagnostic system that allow you to check if a problem occurs inside the unit. It provides convenience and simple troubleshooting, reducing guessing work for both owners and service technicians.

If the heater is equipped with the remote controller and something is wrong with the unit, the three-digit error code will appear. If there is no remote control, the only thing that will indicate the problem will be a green LED on the computer board, which will signal from one to six times.

Using Takagi error codes for troubleshooting

For the proper use of this Takagi error code list including quality repair, we will consider the following: Takagi water heater was properly installed, per codes and manufacturer's recommendations. This includes electric, water, and gas connections and vent flue installation.

Error code 031 (green LED flashes only once)

Problem: The DIP switch setting is incorrect.

Solution: Position the DIP switch according to the manual.

Error code 101 (green LED flashes five times)

Problem: Improper combustion.

Solution: The venting system might be blocked or damaged, or the air intake terminal is too close to the exhaust terminal, so the fumes are getting into the air intake. The burner system might need some cleaning due to the presence of dirt, grease or the unit might be in a contaminated area.

Error code 111 (LED three times flashes)

Problem: Ignition fails.

Solution: Ensure the Hi-Limit switch runs properly, and the wires are not loose or damaged. Clean the flame rod from soot and deposits and make sure the computer board is not damaged and the heat exchanger is not leaking.

Error code 121 (LED flashes three times)

Problem: Flame loss.

Solution: The reasons for the flame loss might be the same as for error code 111 and related to the Hi-Limit switch, wires, flame rod, and computer board.

Error code 311 (LED flashes two times)

Problem: Outlet thermistor.

Solution: Depends on the model, check the outlet thermistor or heat exchanger thermistor and wire connections.

Error code 321 (LED flashes two times)

Problem: Inlet thermistor.

Solution: Check the inlet thermistor, and if broken, replace it.

Error code 331 (LED flashes two times)

Problem: Inlet thermistor.

Solution: Ensure the proper work of the outlet thermistor and, if broken, replace it.

Error code 341 (LED flashes two times)

Problem: Exhaust thermistor failure.

Solution: Replace the exhaust thermistor.

Error code 391 (LED flashes two times)

Problem: Failure of the Air-Fuel ration rod (AFR).

Solution: Check the wire connection for looseness or breakage.

Error code 441 (LED flashes two times)

Problem: Flow sensor.

Solution: Ensure the flow sensor wires are correctly connected and with no damage.

Error code 510 (LED flashes six times)

Problem: Gas solenoid valve malfunction.

Solution: Check wires and computer board for damages.

Error code 551 (LED flashes six times)

 The same as the 510 error code.

Error code 611 (LED flashes four times)

Problem: Fan motor problem.

Solution: Check the connections, wires, and computer board for damages and looseness.

Error code 651 (LED flashes four times)

Problem: Faulty flow adjustment valve.

Solution: Remove the mineral buildup and fix the damaged wire.

Error code 661 (LED flashes four times)

Problem: This error code appears only on 540H models that have an issue with the bypass valve.

Solution: Check the wire connections and ensure the unit is not affected by the limescale build-up.

Error code 701 (LED flashes one time)

Problem: Computer board error.

Solution: Check the wire connections.

Error code 711 (LED flashes one time)

Problem: Gas solenoid valve circuit failure.

Solution: See the error codes 111 and 121.

Error code 721 (LED flashes six times)

Problem: False flame detection.

Solution: Check if the combustion chamber is properly sealed and does the unit drain the condensate (only indoor models).

Error code 741

Problem: The water heater doesn't respond when the remote is used.

Error code 751

Problem: The same problem as for error code 741.

Error code 761

Problem: Easy-Link system miscommunication between the water heaters.

Problem: Exhaust temperature is too high. The maximum temperature of the hot water should be 140 F.

Error code 941 (LED flashes five times)

Problem: Exhaust temperature is too high. The maximum temperature of hot water should be 140 F.

Error code 991 (LED flashes five times)

Problem: Improper gas combustion.

Solution: Check and fix the exhaust and vent system if there are blockages and incorrect air supply. The water heater might not be getting fresh combustion air, especially if it is installed in the contaminated area or intake is too close to the exhaust. Is the unit properly set for the right altitude?

Due to the complexity of Takagi tankless water heaters, you might have to have extensive knowledge and skills to repair the product.

Alternatively, if thinking to call an expert, check out this site first, where you can fill out the online form and get three free quotes from the plumbers in your area, with no obligation or money spent.