On the covered LG range or oven, F21 means a Steam Sensor Failure — LG's own wording. First, note whether a steam function was selected. Then: for F21 LG skips the CLEAR/OFF key: switch the breaker off, wait 30 seconds and switch it on again — LG's own sequence.
Differential
Likely causes of “LG range or oven code F21”, and how to tell them apart
- 1
A steam sensor that has failed
What separates it The code appears when a steam function is selected
How to confirm Note whether a steam or steam-clean cycle was running
- 2
Mineral build-up around the steam parts
What separates it Hard water leaves deposits
How to confirm Look at the water you use and when the code began
- 3
A loose sensor wire
What separates it The code comes and goes
How to confirm A technician checks the connector with power off
- 4
A control that misreads the sensor
What separates it The sensor tests well
How to confirm A technician checks the input on the control
Before you touch a setting
Record this first — changing settings destroys the evidence
- Whether the code is F21, F22, F24 or F25
- Whether a steam function was selected
- The hardness of your water
- Whether the code returns after the breaker reset
Try in this order
0 of 10 completedWhat to do first
ReversibleNote whether a steam function was selected.
Correct only the documented fault domain
ReversibleFor F21 LG skips the CLEAR/OFF key: switch the breaker off, wait 30 seconds and switch it on again — LG's own sequence.
Avoid steam functions
ReversibleDo not repeat the steam or EasyClean function while the code returns.
Wipe the cavity when cool
ReversibleAfter the oven has cooled and the power is off, wipe the cavity floor and look for white mineral residue around the steam area; residue there can upset the sensor.
Use LG's breaker reset
ReversibleTurn the range's breaker off for 30 seconds and back on; LG gives no CLEAR/OFF step for this code.
Avoid steam functions
ReversibleSwitch to ordinary Bake and see whether the oven works normally.
Note your water
ReversibleHard water leaves scale on steam parts; if your kettle scales quickly, say so to the technician.
Wipe the cavity
ReversibleWith the oven cool, remove standing water and residue around the steam outlet.
Keep water away from the electronics
ReversibleNever spray cleaner into the control panel or vents.
Record the cycle
ReversibleWrite the code, the function and the date.
Model-specific
What is true of this model and not of its siblings
- Models
- Only LG ranges and wall ovens with steam features show these codes.
- Water
- Hard water shortens the life of steam parts.
- What LG says
- LG gives the breaker reset and then service.
Stop boundary
When this stops being a self-service repair
- !LG gives a breaker reset for this code with no CLEAR/OFF step; if it returns, book service
- !Do not use the steam function until it is repaired
- !Keep water away from electrical parts
Evidence ledger
Sources behind this answer
Where the manufacturer's article stops. LG words these four codes identically, so they share this page; LG's step for them is the breaker reset only.
Exact questions
Common questions
What does F21 mean on a LG range or oven?+
a Steam Sensor Failure — LG's own wording.
Can I keep baking?+
Ordinary bake may work; avoid the steam function until repaired.
Which display codes point to a failed steam sensor on an LG oven?+
LG words them all as a steam sensor failure, so they share this page.
Is scale to blame?+
It can contribute, because steam parts clog with minerals, but the code names the sensor, not the scale.
Will descaling fix it?+
Only if the manual describes a descale routine for your model; follow it exactly.
Does the breaker reset help?+
It clears a one-off glitch, not a failed sensor.
How do I know whether my oven has steam features?+
Check the control panel for a Steam or Steam Clean key, and the model number against LG's manual; only those models can show this code.
Does the code stop all cooking?+
Often only the steam function is blocked, but the oven may refuse a clean cycle too, so test with an ordinary bake first and see what the display allows.
What should I tell the technician?+
The exact code, the function you were using, whether the cavity had standing water and how hard your water is, which makes the first visit more likely to be the last.
Does the steam sensor affect safety?+
It protects the steam system from running dry or overheating, which is why the oven stops the function when the sensor reads wrongly and shows a code.
How often should I descale a steam oven?+
Follow the manual's schedule; steam ovens in hard water areas usually need regular descaling, and skipping it is a common reason for steam faults.
Will the oven work normally on other settings?+
Usually yes. Bake, broil and convection do not use the steam parts, so you can cook while you wait for service.