Written by
Lena Hartwell Appliance Care EditorPublished October 27, 2026
VERIFIED
Error codeU42 / L42
ApplianceWall Oven
Fault in plain terms
Stored E2 data on the relay board carries a checksum, and the one the board calculates no longer agrees with it. An upper or single oven shows U42; a lower oven shows L42.
How the control tests itself
Each power-up, the checksum is worked out again 5 times.
If there is still no match, the control defaults to a fatal error.
When the start-up test passes, the checksum keeps being watched while the oven operates.
Result
Every function is unavailable. The manual lists a bad relay board as the source and swapping that board as the solution, which makes the next step a call for service.
Documented for
Touch-glass Dacor wall ovens, 27 or 30 inches wide, one or two cavities, series not named.
For U42 or L42, call (415) 687-5926 and describe what happened. Mention the code, the model number and whether it came back after the oven was powered up again. More at Dacor wall oven repair.
Model compatibility: Dacor reuses codes across series and model years, so U42 / L42 may mean something different on another appliance or generation. Confirm this against your model’s documentation and record your full model number before acting.
Plain language
What this code means
Relay board E2 checksum failure: the calculated checksum does not match the stored one.
Important safety warning. Do not attempt repairs involving electrical components, gas, water lines, refrigerant or sealed systems. Unplug the appliance if it is safe to reach the outlet, and leave internal diagnostics to a qualified technician.
Seeing this code on your Dacor appliance?
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