How to Clean O2 Sensors to Pass Smog Tests

by Alibaster Smith

O2 sensors are sensors which measure the toxins that are expelled from your vehicle's exhaust system. The O2 sensor is an emissions control device, and is required in states that use smog testing for annual vehicle inspections. States like California are especially strict with smog testing, so its important to make sure that your vehicle's O2 sensors are functioning properly. While cleaning an O2 sensor is not common, it can be done. If you are successful in cleaning the sensor, the check engine light that comes on as a result of a faulty O2 sensor should go out and your system should pass smog testing.

Step 1

Slide the floor jack under the front jack point of your vehicle. Normally, this will be located behind the radiator.

Step 2

Jack up on the vehicle, place a jack stand under each of the front pinch welds and lower the vehicle onto the stands.

Step 3

Disconnect the cable connected to the negative battery terminal by turning the nut on the cable clamp counterclockwise until the clamp is loose. Then slide the clamp off the battery terminal.

Step 4

Disconnect the electrical connector running to the O2 sensor. The sensor is located either on the catalytic converter or there will be two sensors. One will be located before the catalytic converter and one will be located after the converter.

Step 5

Turn the O2 sensor counterclockwise with an O2 sensor removal tool and pull the sensor out.

Step 6

Hold the O2 sensor with vice grips and heat the sensor end of the sensor with a propane torch until the tip turns slightly red but don't allow the tip to "glow."

Step 7

Submerge the heated end of the sensor into a bucket of cold water once the tip of the sensor turns red. Make sure you are not dipping the entire sensor in the water, but the end that you heated. The rapid heating and cooling will cause the interior of the sensor (which you cannot see directly due to a protective casing) to expand and contract, and is the the only real way to loosen the carbon deposits that have built up on the inside of the sensor.