Alto-Shaam Combi Oven Error Code E94: No Signal to Interface Board
E94 Communication Error, TO Interface Board means no signal passed between the interface board and the control board for over 20 seconds. Power the oven down, reconnect it and restart as the manual describes. If E94 returns, a technician should check the CAN cable and board connectors.
High: the boards are not exchanging signals, so the oven may stop.
- Code
- E94
- Maker
- Alto-Shaam
- Equipment
- Combi ovens
- Applies to
- Combitherm CT PROformance (CTP) and CT Classic (CTC); Combitherm CT Express / ESi / CCi (older 4-10 and 4.10 units; boiler or generator electric/gas)
What does Alto-Shaam error code E94 mean?
The interface board and control board pass signals over a CAN cable constantly. A timer runs whenever nothing arrives. If there is no signal transfer for more than 20 seconds, the control posts E94 Communication Error, TO Interface Board, where TO stands for time-out. Unlike E93, where the boards communicate but disagree, here the line is silent. The manual repeats the restart advice: turn the oven off, disconnect power, reconnect and restart. If it returns, it lists a defective CAN cable, a defective relay board low voltage connector, or a defective display board connector. A cable that is cut, pinched or loose will give a silent link. The CT Express manual lists the same number as a time-out to the display board, so the board named differs while the idea is the same.
Affected models and control systems
Electric and gas CT PROformance and CT Classic ovens in sizes 6-10 through 20-20. The CT Express manual names this TO Display Board.
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
- E94 Communication Error on the display
- Keys not responding or the screen blank
- Oven stopping without warning
Possible causes
Listed in Alto-Shaam's documentation
- CAN cable defective
- Relay board low voltage connector defective
- Display board connector defective
Other likely causes — what usually sits behind error code E94 on this control. A technician confirms which one it is before any part is replaced.
- A CAN cable chafed against a metal edge behind the control panel
- Moisture in a connector after the panel was washed down
Safe checks before calling for service
- Turn the oven off at its switch or breaker and wait about a minute.
- Switch it back on and see whether the display starts normally.
- Do not spray water on or around the control panel.
- If E94 returns, note whether the panel had been cleaned recently and call.
How a technician diagnoses error code E94
- Read the code and confirm the restart was tried.
- Inspect the CAN cable path for pinching or chafing.
- Check the connectors on the relay board and display board for corrosion or looseness.
- Measure the supply to the control electronics.
- Replace the cable first if damaged; boards only after that.
- Connectors and cables are behind the panel next to live voltage.
- Moisture damage must be looked for with the panel open.
- A new board may need configuring for the oven.
How error code E94 differs from similar codes
E92 means the control board does not answer, E93 means mismatched states, and E94 means the link is silent for 20 seconds.
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); Combitherm CT Express / ESi / CCi (older 4-10 and 4.10 units; boiler or generator electric/gas)
- 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
What does TO mean?
Time-out: the signal did not arrive within 20 seconds.
Is E94 the same as E92?
They share causes, but E92 is about the control board not responding.
Can washing the panel cause E94?
Moisture in a connector is plausible; the manual lists defective connectors and cable.
Need help with Alto-Shaam error code E94?
A technician confirms the cause on site and gives you the price in writing before any work starts.