What Are the Symptoms of a Bad 02 Sensor?

In modern cars, electronics control the ratio of air and fuel inside the engine to regulate performance. Sensors are key to maintaining a proper mixture. However, these sensor often break after several years, causing different problems to occur.

Sensor Function

The oxygen sensor on a vehicle is used to reduce emissions and maintain high fuel economy. By sensing the amount of oxygen in the exhaust, the O2 sensor determines the proper mixture of fuel and air inside the engine. A sensor malfunction throws this mixture off.

Fuel Economy

One of the first symptoms of an oxygen sensor malfunction is gas mileage that is higher than normal. Because the engine oxygen ratio is directly affected, bad fuel economy is often a warning sign.

Warning Lights

Generally, a bad O2 sensor will cause the "check engine" light to be displayed. If an otherwise well-maintained vehicle begins showing this indicator, the oxygen sensor is often at fault.

OBDII Codes

Another sign of a malfunctioning O2 sensor is a fault code in the vehicle diagnostic code. This code is called OBDII and can be checked by a parts store or mechanic shop. The displayed code will indicate a problem with oxygen sensors.

Smog Failure

In states that require emissions or smog testing, a failing result can indicate that the vehicle has an oxygen sensor problem. This malfunction causes the engine to burn fuel inefficiently, causing the test failure.

References

• MR2.com: Oxygen Sensor Information
• eBay Guides: O2 Sensor Defective Indicators