Utica Dunkirk E40 Error Code
HRU unit test error problem Parameter incorrectly Find the external problem set
Source: dmg-240__utdu-dmg-240-iom.pdf
What does Utica Dunkirk E40 mean?
E40 on the Dunkirk DMG-240 indicates the HRU (heat recovery unit) or URC unit self-test has failed. The DMG-240 tests the HRU accessory at start-up through the auxiliary SCU board. If the test fails due to a wiring fault, a misconfigured parameter, or a defective HRU unit, the boiler logs E40 and halts operation.
Symptoms
- E40 displayed on the DMG-240 control panel — boiler will not start.
- Fault occurs at start-up during the self-test sequence before burner ignition.
- HRU or URC accessory connected to the auxiliary SCU board is not responding.
- No heating or hot water output while E40 is active.
Common causes
- Wiring connection to the HRU terminal on the auxiliary SCU board is loose or disconnected.
- Parameter P42 is incorrectly set — P42 must be set to 1 when HRU is in use, and 0 when it is not.
- Wiring from the SCU board to the main control board is not secure.
- HRU accessory has failed internally and is not responding to the test signal.
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Diagnostic steps
Verify whether the HRU terminal is in use
Check whether an HRU or URC device is physically connected to the HRU terminal on the auxiliary SCU board per Section 8 of the IOM.
Check wiring connections to the HRU terminal
Inspect the wiring at the HRU terminal on the SCU board. Reseat any loose connectors and check for damaged or broken wires.
Verify wiring from SCU to main control board
Inspect the harness between the SCU auxiliary board and the main control board. Reseat loose connectors at both ends.
Check and correct parameter P42
Navigate to parameter P42 in the installer menu. Set P42 = 1 if an HRU device is connected; set P42 = 0 if no HRU is in use. Incorrect P42 setting is a common cause of E40.
Test the HRU accessory
If P42 and wiring are correct and E40 persists, test the HRU accessory independently. If it is not operating properly, correct or replace the HRU unit.
When to call a professional
Call a licensed technician if parameter P42 changes and wiring corrections do not clear E40, or if the HRU accessory itself requires service or replacement. The SCU board and main control board replacement, and re-running auto-detect, must be performed by a factory-trained technician to avoid additional configuration faults.
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Other Utica Dunkirk Error Codes
,E28,E40,E50,E160,E321,and E431 -Indicate possible faulty components. 53 - Indic
, 78 and 92 - Indicates possible wrong calibration, a new calibration is needed.
,E135 - Indicate the gas supply has been interrupted, ignition has failed or fla
,E 133, E 134,E 135, E 09,E 15,E 128 and E 384 - are displayed it is possible to
Gas Valve Connection Cable 日 10 External Probe Fault 12 Water Flow Switch Open 1
Water Refill Enabled E 19 Max Time Of Water Refill 20 Central Heating Flow NTC F
Flue NTC Fault E40 Central Heating Return NTC Fault Hot Water NTC Fault (tank ve
PCB to be set by the "Calibration Function" E 171 Fan parameter Out of range in
87 Communication error E92 Combustion test alarm during auto-setting E 1 109 Pre
E11 between the supply and return temperatures too Sensor not/poorly connected N
Temperature of heat exchanger is above the normal range (high- limit thermostat
5 burner start-up failures that the air inlet and exhaust flue are not blocked C
Sources: dunkirk.com