The amber “Check Engine” warning lit up on my instrument panel recently.
I took the car to a workshop and was told that my “oh-two” sensor was faulty and had to be replaced.
What exactly is an “oh-two” sensor? Why should I replace it?
Prior to the warning light, there were no problems with my car.
The term “oh-two” comes from the chemical symbol of oxygen, which is O2 .
In a car, the oxygen sensor, also referred to as lambda sensor, is an electrical device that measures the residual oxygen in the exhaust gases.
It is located close to the exhaust manifold.
In newer cars, there is usually a second oxygen sensor further down the exhaust pipe just before the catalytic converter.
An oxygen sensor is made of a ceramic material to withstand extreme temperatures. But it has a lifespan.
As sophisticated as they seem, oxygen sensors are relatively easy to replace.
For most cars, a unit costs less than a tankful of petrol.
The O2 measures the oxygen content after combustion and sends the data to the electronic controller or engine control unit (ECU).
Very precise adjustments are then made by the ECU to the throttle and fuel injection to maintain optimum fuel efficiency and minimise emissions.
Think of it as “fine-adjustment”.
Without the oxygen sensor, the engine will continue to run without showing any obvious signs of degradation in performance.
However, there will be a measurable increase in fuel consumption and a slight increase in emissions which, of course, cannot be detected.
In the long run, the higher fuel bills will indicate a problem.
Since it is relatively inexpensive, just replace the unit to prevent any issues down the road.
If there are two units, you might want to replace both to make sure they work fine.