Alto-Shaam Combi Oven Error Code E06: Lower VFD Comm Failure
E06 Lower VFD Comm Failure means the control board is getting no answer from the lower fan drive on a roll-in oven. Press the Start icon to acknowledge it, and ask for service if it returns.
High: the lower fan cannot be commanded, so the program stops.
- Code
- E06
- Maker
- Alto-Shaam
- Equipment
- Combi ovens
- Applies to
- Combitherm CT PROformance (CTP) and CT Classic (CTC) roll-in models
What does Alto-Shaam error code E06 mean?
Roll-in combi ovens use a second variable frequency drive, or VFD, for the lower convection fan. Like the upper one, it listens to the control board over a CAN cable and is expected to reply. When the lower drive stays silent, the control posts E06 Lower VFD Comm Failure. The manual describes it as the same as E05 but for the lower drive, so the causes are alike: the drive has lost power, its CAN cable has come off, the drive itself has failed, or the control board has failed. The fan may be perfectly sound; the oven simply cannot command it. Pressing Start acknowledges the message and lets the oven try to return to normal operation, but each start repeats the communication check. If E05 and E06 appear together, the shared CAN cable or the control board becomes more likely than either drive alone.
Affected models and control systems
Alto-Shaam Combitherm CT PROformance and CT Classic roll-in combi ovens, for example the 10-20 and 20-20 sizes, electric and gas. Table-top ovens have no lower drive, so this code does not apply to them.
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
- E06 Lower VFD Comm Failure on the display
- Lower fan not starting while the upper fan runs
- Roll-in oven cooking unevenly or refusing to start a program
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 E06 on this control. A technician confirms which one it is before any part is replaced.
- A damaged CAN cable section where the cable bends toward the lower drive
- A lower drive supply fuse or protector that has opened while the upper drive still has power
Safe checks before calling for service
- Press the Start icon once to acknowledge E06.
- See whether the upper fan runs; if it does, only the lower drive is silent.
- Check that the oven's breaker is on and nothing was spilled near the base of the oven.
- If E06 returns, note whether E05 or E08 ever appeared with it, then call.
How a technician diagnoses error code E06
- Read the code, and check whether E05 appears with it to judge a shared CAN problem.
- Verify power at the lower VFD with a meter.
- Inspect the CAN cable and connectors on the lower drive for damage, corrosion or looseness.
- Read the drive's LED for a blink code.
- Swap or replace the drive only after the cable and power are confirmed, and the control board last.
- The lower drive sits low in a roll-in oven where spills can reach its wiring.
- Checking supply and signal on the drive involves live 208-240 V.
- Telling a drive failure from a control board failure needs a known-good part or a communication test.
How error code E06 differs from similar codes
E05 is the table-top or upper drive; E06 is the lower drive, and E08 is the lower drive reporting its own error rather than staying silent.
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) roll-in models
- 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 E06 only on roll-in ovens?
Yes, the lower drive exists only on roll-in models.
Does the oven run on one fan?
It will not cook properly, and the control stops when the lower drive does not answer.
Why does it say Comm and not Fan?
Because the board lost communication; it cannot say whether the fan turns.
Need help with Alto-Shaam error code E06?
A technician confirms the cause on site and gives you the price in writing before any work starts.