An oxygen sensor is one of the most important sensors in a fuel-injected engine. An oxygen sensor looks like a spark plug and is installed in the engine’s exhaust manifold, up system from the catalytic converter. Oxygen sensors come in a few different types including three wire and four wire models. Some oxygen sensors will work on a variety of different engines and some require specialized models.

Older engines usually use an oxygen sensor with a single wire, which is not as durable as newer three and four wire models, and do not warm up as quickly. Engines manufactured after 1990 or so usually have the newer three or four wire oxygen sensor models. If you are going to replace the oxygen sensor in a newer car or you are putting a new engine in a classic car, you will need a three or possibly four wire sensor that is compatible with the engine.

Oxygen sensors must be heated to function, which gives multi wire sensors an advantage over single wire sensors. Multi wire sensors include a 12 volt heater to bring them up to temperature faster than older single wire sensors. This will help to give your vehicle better gas mileage. Three wire oxygen sensors have one wire that is connected to the sensor and two connected to the heater. Four wire sensors have one connected to the sensor, one as a ground wire, and two connected to the heater.

Installing an oxygen sensor in your car is not one of the easiest maintenance tasks to perform, but it can be accomplished by most anyone with some automobile experience. You will need some special tools such as a welding gun, and a lift will make working on the underside of the car easier. Replacing an existing oxygen sensor is easier than installing a new one on an engine that you have converted as you will have the old one to use as a reference for location and position.

You should make sure you install the new oxygen sensor the same distance from the exhaust as the old one, if you are installing the oxygen sensor for the first time, find out exactly where along the exhaust it should be located. You must then bolt the sensor’s headers to the car leaving enough ground clearance for the sensor without putting it so high that it will hit the underside of the car. You will need to drill a pilot hole for the sensor and then a larger one for the bung to fit in to. After you have fitted the sensor into the hole you will need to weld it into place. The last step is to connect the wires; if you are using a three wire oxygen sensor then you will need one to connect to the signal and two to the heater. If you are using a four wire sensor than one will be connected to the signal, one will be ground, and two will be for the heater.