Exhaust
What is an Oxygen (O2) Sensor?
Tells the ECU if the fuel mixture is right.
Simplified animation — not to scale.
In plain English
A small probe screwed into the exhaust pipe that measures how much unburnt oxygen is leaving the engine.
A simple analogy
"It is the exhaust's taste tester — checks what just came out of the engine and tells the brain to adjust the recipe."
How it works
The reading tells the ECU whether the engine is running rich (too much fuel) or lean (too much air), so it can constantly tweak the injectors to keep the mixture spot on.
Signs of trouble
- ⚠Check engine light on
- ⚠Poor fuel economy
- ⚠Rough idle or hesitation
- ⚠Failed MOT emissions test
Rough UK cost
£80–£350
Parts: £40–£200
Labour: £40–£150
Always get a written quote. Prices vary by car, region, and parts brand.
Heads up: Carautonomy is for general guidance only. If your car is showing warning lights or behaving oddly, get it looked at by a qualified mechanic.