Origination

• Bosch engineers introduced the oxygen sensor in 1976 in the Volvo 240/260, in answer to the concern about emissions in California.
  
  

Purpose

• The oxygen sensor rests in the fuel exhaust stream and measures the amount of unburned oxygen being released from the car. The sensor reports this information back to the computer, which adjusts the fuel mixture to increase power and fuel efficiency and decrease emissions. The sensor works with the catalytic converter.
  
  

Malfunction

• Oxygen sensors diminish in performance with age. If fuel economy drops or emissions increase, your oxygen sensor could be malfunctioning. Inspect the sensor when you change spark plugs to ensure it continues to do its job. Test the sensor with a digital voltmeter and replace as necessary.