Convotherm Combi Oven Error Code E99: Communications Dropped Out
E99 on a Convotherm C4 means communications inside the oven dropped out. Disconnect the unit from the outlet for about 10 seconds and restart it. If E99 comes back, it needs a service call.
Medium: the oven may stop mid-program, but a restart often restores it.
- Code
- E99
- Maker
- Convotherm
- Equipment
- Combi ovens
- Applies to
- Convotherm 4 (C4 easyTouch / easyDial, incl. Maxx pro)
What does Convotherm error code E99 mean?
A combi oven is not one board but several: the display, the main control and the boards that switch the fan, heating and valves all pass messages to each other many times a second. The control expects those messages to keep arriving. When the link goes quiet, for example after a power dip or because a connector has worked loose, the oven cannot trust what it is told about its own state and it stops with E99 Communications dropped out. Because the check is about the conversation between boards and not about a single sensor, the code does not say which board stopped answering. The manual treats it as something a restart can sometimes clear: disconnect the unit from the outlet for about 10 seconds so every board powers down fully, then plug it back in. A power cycle clears a one-time interruption. A link that drops again after a restart points to a connector, cable or board, and that is a job for service.
Affected models and control systems
Floor-standing Convotherm 4 (C4) combi ovens, taken from the UL / USA operating manual; table-top and maxx pro units are not mentioned in the part we read.
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
- E99 Communications dropped out on the display
- Oven stops or will not start a program
- Display frozen, blank or restarting
- Message returns after a restart
Possible causes
Likely causes — what usually sits behind error code E99 on this control. A technician confirms which one it is before any part is replaced.
- Brief power dip or surge on the oven's circuit
- Loose ribbon cable or connector between the display and main control
- Moisture or grease reaching a connector behind the panel
- Main control board that intermittently stops responding
Safe checks before calling for service
- Turn the oven off and unplug it from the outlet.
- Wait about 10 seconds, then plug it back in and restart.
- Run a short program to see if the oven behaves normally.
- If E99 returns, stop and contact Customer Service; do not keep cycling the power.
- Note when it appears, such as at startup or during a cycle, and whether lights flicker in the kitchen.
How a technician diagnoses error code E99
- Read the E99 code and history to see how often the link drops and under what load.
- Check incoming voltage and the outlet or breaker feeding the oven for dips.
- Inspect the connectors and cable between the display and the main control for looseness or moisture.
- Check the board connections and grounds in the control compartment.
- Swap or reseat the suspect board only after the connections test clean.
- The communication cables run beside line-voltage wiring in the control compartment, so inspecting them means working next to live parts.
- A dropping link can come from a board, a cable or the power feed, and telling them apart takes service tools.
- Replacing a control board also means loading the oven's own settings back correctly.
How error code E99 differs from similar codes
E99.9 is the start-up version of the same family: it reports an initialization error and has the same unplug-and-restart response.
Technical reference
- Maker documentation
- Convotherm owner support
- Edition
- 9761695_06 engUSA 05/22
- Models / control
- Convotherm 4 (C4 easyTouch / easyDial, incl. Maxx pro)
- Section
- 6.2.1 Error codes (Errors and required responses), pp. 105
- 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 Convotherm combi oven error codes
Is E99 the same as E99.9?
They are separate messages with the same first response. E99 reports lost communication; E99.9 reports an initialization error.
Will E99 clear if I just wait?
Not usually. The manual's step is to disconnect the oven for about 10 seconds and restart it.
Is a power outage the likely reason?
It can be. A short dip in power is a common way for the link to drop, but if E99 repeats, the link itself needs checking.
Need help with Convotherm error code E99?
A technician confirms the cause on site and gives you the price in writing before any work starts.