Alto-Shaam Combi Oven Error Code E20: B11 Core Probe Failure
E20 B11 Core Temperature Probe Single Point Fault means the single-point core probe, B11, is defective or not connected. Press the Start icon to acknowledge it, push the probe fully into its receptacle, and call if the message returns.
Low: only the core probe feature is affected, and time-based cooking can continue.
- Code
- E20
- 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 E20 mean?
Some cooking programs run on the food's internal temperature instead of time. The single-point core probe, B11, is plugged into a receptacle in the cavity and the control reads its signal. If the signal says the probe is open, shorted or missing, the control posts E20 B11 Core Temperature Probe Single Point Fault. The manual lists four causes: the probe is not inserted correctly, it is not connected to the oven, the receptacle pins are dirty, or the probe has failed. The first three are things an operator can look at. Pressing Start acknowledges the message and the oven tries to return to normal operation, but a program that depends on the core probe will not trust a bad signal. Note that the CT Express manual lists E20 as HACCP-only, so other ovens may show it in a different context.
Affected models and control systems
CT PROformance and CT Classic combi ovens, electric and gas, sizes 6-10, 10-10, 7-20, 10-20, 20-10 and 20-20 that use the single-point core probe. For the CT Express, the manual treats E20 as a HACCP-only 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
- E20 core probe message on the display
- Core temperature program not starting or stopping at once
- Probe reading missing from the screen
Possible causes
Listed in Alto-Shaam's documentation
- B11 probe not inserted correctly
- B11 not connected to oven
- Dirty receptacle pins
- B11 malfunction
Other likely causes — what usually sits behind error code E20 on this control. A technician confirms which one it is before any part is replaced.
- A bent probe plug that no longer seats fully in the receptacle
- A cracked probe cable from being closed in the oven door or hung on a hot rack
Safe checks before calling for service
- Press the Start icon once to acknowledge E20.
- Check that the probe plug is pushed fully into its receptacle.
- With the oven cool, look at the plug and pins for grease or food residue and wipe the plug clean.
- If E20 returns, run the program on time instead of core temperature and give the technician the probe's age.
How a technician diagnoses error code E20
- Read the code and confirm which core probe the program uses.
- Check the probe plug, cable and receptacle pins for damage and residue.
- Clean the pins and reseat the probe.
- Meter the probe resistance at room temperature against its chart.
- Replace B11 or the receptacle wiring only if the clean, reseated probe still fails.
- The receptacle wiring connects to the control board inside the oven.
- A probe that reads near correct but drifts needs a resistance check at known temperatures.
- Programs that rely on core temperature affect food safety, so a doubtful probe should be tested properly.
How error code E20 differs from similar codes
E21 concerns the cavity probe N6 and E22 the multipoint probe B10, while E20 names only the single-point probe B11.
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
Can I cook by time while E20 shows?
Yes, a time-based program does not need the core probe, though you should note the code for service.
Does E20 mean the probe is broken?
Not always. It is often not seated or dirty at the pins, which are the first three causes listed.
Is E20 the same as E22?
No. E22 is the multipoint probe B10.
Need help with Alto-Shaam error code E20?
A technician confirms the cause on site and gives you the price in writing before any work starts.