Alto-Shaam Combi Oven Error Code E05: VFD Comm Failure
E05 VFD Comm Failure means the control board got no answer from the table-top or upper fan drive (VFD) on the CAN interface. Press the Start icon to acknowledge it, and call service if it returns.
High: with no answer from the drive the convection fan cannot run.
- Code
- E05
- Maker
- Alto-Shaam
- Equipment
- Combi ovens
- Applies to
- Combitherm CT PROformance (CTP) and CT Classic (CTC)
What does Alto-Shaam error code E05 mean?
The convection fan is run by a variable frequency drive, or VFD, which takes its speed commands from the control board over a CAN communication cable. The board sends a message and expects the drive to answer. When no reply comes back from the table-top or upper VFD, the control posts E05 VFD Comm Failure. That does not say the fan is stuck. It says the two electronics are not talking. The manual's causes are that the VFD lost power, the CAN cable came disconnected, the VFD failed, or the control board failed. After you press Start the oven tries to return to normal operation, but the drive has to answer for the fan to run, so the code returns until the link is restored. Roll-in ovens have a second drive for the lower fan, which has its own code, E06.
Affected models and control systems
The CTP and CTC series of Combitherm ovens, 6-10 through 20-20, electric or gas. E05 is the number for the table-top oven's drive or the upper drive of a roll-in.
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
- E05 VFD Comm Failure on the display
- Convection fan not starting when a program begins
- Display and keypad working normally while the fan stays idle
Possible causes
Listed in Alto-Shaam's documentation
- Loss of power to the VFD
- CAN cable disconnected
- VFD malfunction
- Control board malfunction
Other likely causes — what usually sits behind error code E05 on this control. A technician confirms which one it is before any part is replaced.
- A CAN cable connector worked loose by vibration after the oven was moved or cleaned
- A tripped or off breaker supplying only the drive circuit
Safe checks before calling for service
- Press the Start icon once to acknowledge E05.
- Check that the oven's breaker or disconnect is fully on.
- Note whether the display and lights work, to tell a total power loss from a drive-only problem.
- If E05 returns, write down the exact time and any recent cleaning or moving of the oven, then call.
How a technician diagnoses error code E05
- Read the code and confirm the oven has a table-top or upper VFD.
- Check the supply to the VFD with a meter.
- Inspect the CAN cable and its connectors at both ends for damage and seating.
- Check the VFD status LED and look up any blink code.
- Replace the VFD or the control board only after the cable and supply are proven good.
- The VFD operates from live 208-240 V and holds charge after power is switched off.
- Testing a CAN link means opening the control area and handling connectors on both boards.
- Replacing a drive or control board needs the oven's own settings reloaded.
How error code E05 differs from similar codes
E06 is the same communication check for the lower VFD, and E07 means the VFD answered but reported an error with its own LED.
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 E05 the same as a fan motor error?
No. E03 and E04 say a motor did not turn; E05 says the drive did not answer.
Can E05 clear after a reset?
It may if the loss was brief, but a loose cable or failing drive usually brings it back.
Does E05 mean the control board is bad?
It is only one of four listed causes, and the cable and power are easier to rule out first.
Need help with Alto-Shaam error code E05?
A technician confirms the cause on site and gives you the price in writing before any work starts.