Rational Combi Oven Error Code 42: Bottom Burner Not Igniting
Ignition controller error 42 on a floor-standing gas SelfCookingCenter or iCombi oven means five unsuccessful ignition attempts were made on the bottom hot air burner. Make sure the gas valve to the oven is open and never try to relight the burner yourself. Tell us the number shown and leave the covers on.
High: the bottom burner will not light, and repeated errors lock the oven out of cooking.
- Code
- Ignition controller error 42
- Maker
- Rational
- Equipment
- Combi ovens
- Applies to
- Automatic ignition controller (SCC / iCombi gas units)
What does Rational Ignition controller error 42 mean?
The bottom hot air burner of a floor-standing gas Rational oven has its own ignition sequence. The automatic ignition controller opens the valve, fires the igniter and watches for flame, and it repeats the attempt if none appears. Error 42 means five such attempts were made and failed, so the controller stopped and the bottom burner stays off until it is checked. Service 140 counts this as a critical gas error, so it can eventually lock cooking. The listed reasons are loose sensing wires or a worn electrode on the bottom burner, a bottom burner gas valve that opens poorly, an ignition controller that fails five start attempts, and a restricted gas supply to the bottom burner. A closed supply valve looks the same on the display as a worn electrode, so that is the first thing to check from outside the oven. The top burner may still work, but the oven is not meant to run on one burner with critical errors showing, and relighting by hand is unsafe.
Affected models and control systems
This applies to floor-standing gas Rational SelfCookingCenter and iCombi ovens with the automatic ignition controller, per Technical Information TI_2220. Error 22 is the top burner counterpart.
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
- Ignition controller error 42 on the display
- No heat from the bottom burner
- Ignition attempts with no flame
- A Service 140 message after repeated errors
Possible causes
Listed in Rational's documentation
- Loose sensing wires or a worn electrode on the bottom burner
- Bottom burner gas valve that opens poorly
- Bottom burner ignition controller that fails five start attempts
- Restricted gas supply to the bottom burner
Other likely causes — what usually sits behind Ignition controller error 42 on this control. A technician confirms which one it is before any part is replaced.
- Shut-off valve partly closed after a gas line service
- Spill residue covering the bottom electrode and blocking the spark
- Low line pressure when several gas appliances run together
Safe checks before calling for service
- Make sure the gas valve to the oven is open, and close it if the message keeps returning.
- If gas is in the air, walk out and phone the utility from outside.
- Never try to relight the burner yourself.
- Tell us the number shown. The covers stay on.
How a technician diagnoses Ignition controller error 42
- Read the error log and the Service 140 count.
- Verify gas supply, pressure and the valve position.
- Inspect the bottom burner electrode, igniter and sensing wires.
- Watch an ignition attempt for spark and valve opening.
- Test the gas valve and the controller output.
- Replace the failed part and confirm ignition with a leak check.
- Bottom burner ignition involves high voltage and an open gas path inside a closed chamber.
- Gas pressure and valve tests require a manometer and a leak detector.
- Manual relighting of a gas burner is dangerous and not part of the maker's instructions.
How Ignition controller error 42 differs from similar codes
Error 42 is the bottom burner failing to light. Error 22 is the same on the top burner.
Technical reference
- Document
- Technical Information TI_2220 New gas service messages 140
- Edition
- TI_2220_en-GB V02.1, 05/2023 (sheet dated 21/09/2022, series 2022/20)
- Models / control
- Automatic ignition controller (SCC / iCombi gas units)
- Section
- Trigger criteria and warning levels, printed pp. 1-2 of 4 (Service 140.4 / 140.8); ignition controller error list 17, 18, 22, 37, 38, 42 on p. 3-4 near the end of the sheet
- 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 Rational combi oven error codes
Why does a closed gas valve cause error 42?
The controller only sees that no flame appeared after five tries and cannot tell why.
Can I light the burner by hand?
No. Do not try to relight it yourself.
Will the oven work on the top burner?
It may, but we advise against it while critical errors are showing.
Need help with Rational Ignition controller error 42?
A technician confirms the cause on site and gives you the price in writing before any work starts.