Alto-Shaam Combi Oven Error Code E104: Option Board Not Communicating
E104 Option Board Not Communicating means the option board is not communicating with the control board. A technician should check the CAN cable, the control board dip switch and the software on both boards.
Medium: option board features are lost until the link is restored.
- Code
- E104
- Maker
- Alto-Shaam
- Equipment
- Combi ovens
- Applies to
- Combitherm CT PROformance (CTP) and CT Classic (CTC)
What does Alto-Shaam error code E104 mean?
The option board adds features to the combi oven and shares a CAN cable with the control board. The control board polls it regularly and expects an answer. When no communication comes back, the control posts E104 Option Board Not Communicating. The manual lists five checks in a sensible order. First the CAN cable from the option board to the control board. Then the dip switch on the control board, which must be ON whenever an option board is fitted. Then the software on the two boards, which must be compatible, with an update if it is not. Only after those does the manual say to replace boards: the option board or the control board. Because the message is about a link, not about heat or water, ordinary cooking can continue in many cases, but the added features will not work. E103 is a close relative that reports the missing switch setting.
Affected models and control systems
Alto-Shaam Combitherm CT PROformance and CT Classic combi ovens fitted with an option board, in sizes 6-10, 10-10, 7-20, 10-20, 20-10 and 20-20. On CT Express ovens E104 means an ignition failure, which is a different message.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- E104 Option Board Not Communicating on the display
- Optional functions not available
- Message returning at each start
Possible causes
Listed in Alto-Shaam's documentation
- CAN cable between option board and control board
- Control board dip switch not ON
- Incompatible option board and control board software
- Option board malfunction
- Control board malfunction
Other likely causes — what usually sits behind error code E104 on this control. A technician confirms which one it is before any part is replaced.
- A CAN connector left unseated after a board was swapped
- A dip switch moved during earlier service and never set back
Safe checks before calling for service
- Turn the oven off and on again once.
- Do not open the control cover to look at boards.
- Note whether the option features work at all after start-up.
- Give the technician the date any board or software was changed.
How a technician diagnoses error code E104
- Read the code and ask what was changed recently.
- Check the CAN cable between OB and CB for seating and damage.
- Confirm the control board dip switch is ON.
- Compare software versions and update if they do not match.
- Replace the option board, then the control board, only if the earlier checks pass.
- Dip switches and cable plugs are on boards inside the live control area.
- Software matching requires the right files and tools.
- Board swaps need to be configured for the oven.
How error code E104 differs from similar codes
E103 reports the option board not sending its switch setting; E104 reports no communication at all. CT Express E104 is an ignition failure.
Technical reference
- Maker documentation
- Alto-Shaam owner support
- Edition
- MN-35949 Rev 08 03/22
- Models / control
- Combitherm CT PROformance (CTP) and CT Classic (CTC)
- Section
- Error Codes, pp. 25-31
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Alto-Shaam combi oven error codes
Is E104 the same as E103?
They have the same causes, but E103 refers to the switch setting not being sent.
Will cooking stop?
The message concerns the option board's link, not heating.
Could software cause it?
Yes, incompatible software on the two boards is a listed cause.
Need help with Alto-Shaam error code E104?
A technician confirms the cause on site and gives you the price in writing before any work starts.