Rinnai Non-SENSEI Code 03
Power interruption during bath fill. Power to the heater, or the link to its controller, was interrupted part-way through the bath fill function. Nothing has failed. Rinnai assigns this code across all three generations with the same meaning and the same two-press reset, so it is one of the few numbers on this site that does not change with the series.
DIY fixThe verdict
No parts needed — reset or re-check a setting
Free to clear, and the reset is the same on this generation as on the newer ones. Rinnai only points at the PC board if code 03 returns after three resets — so reset first, and treat a fourth appearance as the signal to call someone.
Typical cost: $0–$700
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-SENSEI — not averaged across the brand.
Source: Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes (100000652) (p. 9), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Turn off every hot water fixture in the house, including the tub you were filling.
- Press the ON/OFF button on the temperature controller twice. That clears the code.
- Run a hot tap and confirm the unit fires normally.
- If code 03 comes back after three resets, stop resetting and book a service call — the PC board is the next suspect and it is a professional replacement.
Code 03 on other Rinnai series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: