How to Check an O2 Sensor

O2 sensors (also called oxygen sensors) are electronic devices that monitor the air-fuel ratio and emission output of your vehicle. O2 sensors help vehicles run efficiently and idle smoothly. A faulty O2 sensor can drastically reduce your fuel economy and engine performance. Learn to check your O2 sensor without paying a diagnostic fee to a service shop.

Things You'll Need

• OBD-II code scanner
• Computer
• Internet access

Instructions

1. 

   Turn the ignition in your vehicle in the "ON" or "ACC" position, without cranking the engine. Locate the female connection module to your vehicle. It is usually located in the driver's side foot-well, visible underneath the steering wheel.

2. 

   Connect the OBD-II (on-board diagnostics) code scanner to the connection module. Once your scanner has verified connection, press the "Scan" button to search for error codes within your vehicle's diagnostic system. A faulty O2 sensor will send an error code to the vehicle.

3. 

   Write down the error codes your scanner displays. If you do not have any error codes, your O2 sensor is fine. The error code for a faulty O2 sensor varies with each brand of vehicle. Access your computer and visit www.obd-codes.com/trouble_codes. (See the resource below for link.)

4. 

   Select the manufacturer of your vehicle and input the error code you received. You will receive a description of the code and whether it applies to your O2 sensor or not. If the codes relate to your O2 sensor, it will have to be replaced.

Tips & Warnings

• An OBD-II code scanner can be purchased for about $70. If you do not want to invest in a scanner, bring your vehicle to an automotive parts store; they will usually check the error codes for you free of charge. You will still have to look them up.

• Even if the error codes for your vehicle are not related to the O2 sensor, it is recommended to have the problem looked at by a mechanic.

References

• Sensor Codes
• Sears OBD II Scanner Price

Resources

• OBD-II Trouble Codes