Utica Dunkirk E02

What does Utica Dunkirk E02 mean?

E02 on the Utica-Dunkirk DMG-240 condensing boiler indicates the supply water temperature sensor has a short circuit — the sensor is reading an extremely low resistance value, which corresponds to an impossibly high temperature. The control board rejects this reading as invalid and locks out the boiler because it cannot safely control supply temperature without a valid sensor input.

Symptoms

• Boiler display shows E02 immediately on startup or mid-cycle
• Boiler locks out with no heating or hot water output
• Supply temperature on the display may read excessively high or dashes
• Fault persists after reset if sensor remains shorted

Common causes

• NTC sensor internal short circuit (sensor failure)
• Wiring harness shorted — two conductors pinched together or to ground
• Moisture ingress at the sensor connector creating a conductive path
• Sensor incorrectly installed with its body grounded to the pipe fitting

Diagnostic steps

1. 01

   Disconnect the supply NTC sensor and measure resistance

   With the boiler powered off, disconnect the sensor connector and measure resistance across the sensor terminals. A near-zero reading confirms the sensor is shorted and must be replaced.

2. 02

   Inspect the wiring harness for shorts

   Check the harness between the sensor and the PCB for pinched sections, chafed insulation, or cable ties that could force the wires together. Repair any damaged sections.

3. 03

   Check for moisture at the sensor connector

   Inspect the sensor connector and PCB header for corrosion or water ingress. Dry thoroughly and apply contact-rated electronic cleaner before reconnecting.

4. 04

   Replace the supply NTC sensor

   Install an OEM replacement NTC sensor, ensuring the body is correctly inserted into the pipe pocket without grounding to the pipe fitting. Reconnect the harness firmly.

5. 05

   Reset and test

   After sensor replacement, restore power, press RESET for 2 seconds, and verify the supply temperature reading is within the expected range for the current system temperature.

When to call a professional

Sensor replacement on the DMG-240 is within the scope of a qualified technician. If E02 returns after replacement, the PCB supply sensor input circuit is shorted internally and requires PCB replacement — a task that must include full calibration commissioning. Contact Utica-Dunkirk technical service for guidance on PCB replacement procedures.