Alto-Shaam CT Express Combi Error Code E104: Gas Ignition Failure
E104 Ignition Failure means the gas burner attempt for ignition failed. Check that the gas supply is on, and call for service if it returns, because the gas pressure, valve, igniter and flue need testing.
High: the gas burner will not light, so the oven cannot heat.
- Code
- E104
- Maker
- Alto-Shaam
- Equipment
- Combi ovens
- Applies to
- CT Express 4-10ESi, 4-10ESiVH, 4-10CCi, CTX4-10E, CTX4-10EC, CTX4-10EVH
What does Alto-Shaam error code E104 mean?
On a gas CT Express, the ignition control tries to light the burner when the oven calls for heat. It opens the gas valve, makes a spark through the igniter wire, and then checks for flame through the flame sense wire. If the attempt fails, the control posts E104 Ignition Failure. The manual lists eight causes: gas supply disconnected or off, gas pressure too low or too high, gas valve not energized, ignition control making no spark, a defective spark wire or igniter, a defective flame sense wire, a defective ignition control, and a blocked flue pipe. The manual's actions are to check the gas supply and pressure, the gas valve, the ignition control, the spark wire or igniter, flame sense and the flue pipes. Gas pressure that is too high is on the list as well as too low, so a regulator problem can also stop a light. This number is specific to the CT Express controller; CT PROformance and CT Classic ovens use E104 for an option board message.
Affected models and control systems
Alto-Shaam Combitherm CT Express ovens, models 4-10ESi, 4-10ESiVH, 4-10CCi, CTX4-10E, CTX4-10EC and CTX4-10EVH, gas-fired versions.
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
- E104 Ignition Failure on the display
- Burner not lighting
- Clicking or a spark sound with no flame
Possible causes
Listed in Alto-Shaam's documentation
- Gas supply disconnected or off
- Gas pressure too low or too high
- Gas valve not energized
- Ignition control makes no spark
- Spark wire or igniter defective
- Flame sense wire defective
- Ignition control defective
- Flue pipe blocked
Other likely causes — what usually sits behind error code E104 on this control. A technician confirms which one it is before any part is replaced.
- A shared gas line that loses pressure when other kitchen equipment fires at the same time
- Soot or a bird nest in an outside flue termination
Safe checks before calling for service
- Check that the gas valve to the oven is open.
- Turn the oven off and on once.
- If you smell gas, leave the area and call your gas provider; do not try to light the oven.
- If E104 returns, tell the technician how many times it tried to light.
How a technician diagnoses error code E104
- Read the code and confirm the oven is gas.
- Measure gas supply pressure at the oven with the burner calling for heat.
- Check for voltage at the gas valve and whether the ignition control makes a spark.
- Inspect the spark wire, igniter and flame sense wire.
- Check the flue pipes for blockage before replacing the ignition control.
- Gas valves and burners need leak-tested repairs.
- The ignition control and spark circuit carry high voltage.
- A blocked flue is a combustion safety issue.
How error code E104 differs from similar codes
On the CT PROformance and Classic, ignition failures are E88 and E89 with a three-strike rule, and E104 there means an option board message.
Technical reference
- Document
- Combitherm CT Express Technical Manual (4-10ESi, 4-10ESiVH, 4-10CCi, CTX4-10E, CTX4-10EC, CTX4-10EVH)
- Maker documentation
- Alto-Shaam owner support
- Edition
- MN-36008 (Rev. 9) 03/16
- Models / control
- CT Express 4-10ESi, 4-10ESiVH, 4-10CCi, CTX4-10E, CTX4-10EC, CTX4-10EVH
- Section
- Section C, Error Codes, pp. C-3 to C-8
- 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 E104 an error I can reset?
You can switch off and on once, but repeated tries are not advised on a gas oven.
Can high gas pressure cause it?
Yes, too high is listed as well as too low.
Is the flue part of this?
Yes, a blocked flue pipe is one of the eight causes.
Need help with Alto-Shaam error code E104?
A technician confirms the cause on site and gives you the price in writing before any work starts.