Noritz NRCP Eco TOUGH Code Er31
Cold water thermistor open or short. The cold water inlet sensor is open or short circuit. Noritz groups four sensor codes with one set of remedies on this generation: check the temperature sensor and that connections are secure, check the sensor resistance and replace it if the resistance is zero, and contact technical support. Auto reset.
Also displayed as: 31, E31
Part replacementThe verdict
Replace a part
Cheap sensor, quick job, inside the cabinet of a gas appliance so it is a service call. Noritz marks it auto reset, which means the code may vanish and come back rather than staying put — note when it happens.
Typical cost: $120–$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 NRCP Eco TOUGH — not averaged across the brand.
Source: Noritz Service Manual — NRCP1112-DV / NRCP982-DV Eco TOUGH (Rev. 05/19) (p. 58), read Sep 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Note when the code appears and disappears — an intermittent sensor fault usually means a connector rather than the sensor.
- Book a service call.
Code Er31 on other Noritz series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit:
Don't confuse this with
3 other Noritz NRCP Eco TOUGH codes point at a thermistor too. They are different components in different places, and ordering a part against the wrong one is the most common way this fault gets expensive: