O2 sensor

I’m looking at a used Chev. Silerado however the owner says the check engine light stays on because of the O2 sensor. what is this and what would be an estimate to fix?

Stay away from this vehicle. Chances are this truck needs something more expensive like a new catalytic converter. Sometimes the computer will throw the same code for a bad sensor as a bad catalytic converter. The error code itself just means the sensor doesn’t like what it sees, which can have many causes. Also, an owner that would not change out an Oxygen sensor and ignore the problem probably doesn’t take good care of the vehicle overall.

If all it really needs is an Oxygen sensor, they can cost between $79 and $300 to replace. It is usually an easy do-it-yourself job.

The O2 sensor measures the oxygen content in the exhaust gas. From this the computer adjusts the fuel mixture. There’s also a second O2 sensor located after the catalytic converter that monitors the catalytic converters efficiency.

The owner may be telling you that the Check Engine light is on because of a defective O2 sensor, but before making the purchase, ask if you can take the vehicle to have the computer scanned for codes. Auto Zone parts stores will do this for free. You want to make sure the Check Engine light isn’t on because of a defective catalytic converter, which is very expensive to replace.


Don’t take the owner’s word for this. There are DOZENS of reasons for a Check Engine light to be on. It may be an O2 sensor and it may not.

I don’t recommend buying any vehicle while its check engine light is on. The light should come on when you turn the key to “ON,” but it should go off as soon as the engine starts. If it doesn’t, find another vehicle.

I agree that you should not simply take the seller’s word on the cause of this problem at face value.
The 02 sensor is probably the most blamed item on a car whenever a CEL comes on.

It could be an O2 sensor or something more seriousness; say coolant leaking into the combustion chambers for one (head gasket, intake gasket), oil burning for another (moderate to major engine problems), etc, etc.