Noritz NRCP Code Er31
Cold water thermistor open or short. The cold water inlet sensor is open circuit or short circuit. Noritz groups four thermistor codes together in this table with one shared set of remedies: check the sensor and its connectors, check its resistance, and replace it if the resistance is open or short.
Also displayed as: 31, E31
Part replacementThe verdict
Replace a part
Cheap sensor, quick replacement, inside the cabinet of a gas appliance so it is a service call. The unit needs this reading to decide how much heat to add, so it is worth fixing rather than living with.
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 — not averaged across the brand.
Source: Noritz Service Manual — NRCP111-DV / NRCP98-DV (Rev. 09/19) (p. 62), read Sep 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Book a service call. Noritz's remedy is to check the connector, measure the resistance, and replace the sensor.
Code Er31 on other Noritz series
Other Noritz series report code Er31 under the same fault name, but each manual is transcribed separately and they do not read alike:
Don't confuse this with
3 other Noritz NRCP 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: