Signs of a Bad Oxygen Sensor

Signs of a bad oxygen sensor should not be dismissed. The oxygen sensor monitors exhaust gases and provides information to the onboard computer that optimizes the air/fuel mix. Properly functioning sensors decrease harmful emissions and increase fuel efficiency.

Oxygen Sensor Troubleshooting

There are actually two oxygen sensors in modern cars. The front oxygen sensor is mounted in the exhaust manifold down pipes, ahead of the catalytic converter. The front sensor guides the onboard computer to provide the most efficient mix of air and fuel. The rear oxygen sensor is located after the catalytic converter in the exhaust system. The rear sensor monitors the efficiency of the catalytic converter.

Oxygen sensors operate in an extreme environment and are subject to exposure to harmful deposits if there are problems with other systems in the engine. Here are some ways to tell if you're experiencing an oxygen sensor problem:

• Less efficiency. A faulty oxygen sensor can cause a drop in fuel efficiency. The incorrect reading supplied by the sensor can cause the air fuel mixture to become too rich, wasting fuel.
• Loss of power. The incorrect fuel mixture caused by a bad oxygen sensor can lead to hesitation, surging or sluggish acceleration.
• Idiot lights. Although you may get a "check engine" light when an oxygen sensor is ready for its scheduled replacement, you may get a different light if the unit actually fails, Check your owner's manual to determine which type of light you're seeing.
• That's hot! A faulty front oxygen sensor can cause the catalytic converter to run at a much higher temperature than normal. An overheated converter will cause the floorboards to be warm and may even glow red with heat. This overheating can quickly damage the catalytic converter, leading to a costly repair.
• Emissions testing. A bad oxygen sensor can lead to an emissions test failure. A study by the US Environmental Protection Agency found that oxygen sensor replacement was required on about half of all vehicles that failed emissions testing.