Takagi Non-Condensing Code 031
Incorrect DIP switch settings. The DIP switches on the computer board are in a combination the heater does not accept. Gas type is the setting most often wrong, and it is the one that matters most. On a T-K4 or T-KJr2 this shows as 03 on the remote, or one flash of the red LED.
Also displayed as: 03
Call a proThe verdict
Call a licensed plumber
A configuration fault rather than a broken part, which normally makes it cheap — but one of those switches sets the gas type, and that is not a setting to experiment with. If the unit was installed, converted, or serviced recently, call that installer back.
Typical cost: $0–$400
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the Non-Condensing — not averaged across the brand.
Source: Takagi Non-Condensing Models On-Demand Water Heater Troubleshooting Guide (p. 12), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
Before anything else: if you smell gas, stop here, leave, and call your gas utility.
- If the unit was installed, converted between fuels, or serviced recently, contact whoever did that work.
- Find out what your house actually runs on: natural gas from a meter, or propane from a tank.
- Do not open the unit to change switch settings yourself.
Frequently asked questions
My unit shows 03, not 031.
Same fault. Takagi's table gives three columns: 031 on a T-D2's display, 03 on a T-K4 or T-KJr2 remote, and one red LED flash if no remote is fitted. Which you see depends on the model, not on the problem.
Code 031 on other Takagi series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: