Monday, March 10, 2014
Installing an Oxygen Sensor
Oxygen Detection
The oxygen sensor informs a car computer of the level of oxygen being burned into the fuel. The computer utilizes this information to regulate the mixture of fuel to oxygen. Installing the oxygen sensor in the exhaust manifold allows the amount of O2 in the fuel mixture to be measured. A zirconium ceramic bulb (enameled in a layer of platinum with oxygen holes) is attached to the end of the oxygen sensor (At the end where the sensor is bolted into the exhaust manifold). Two leads platinum electrodes reside inside of the bulb. A very small amount of space is provided for the insulation and the wire. Air must be allowed to reach the oxygen sensor. When installing the oxygen sensor, no grease is used (grease inhibits the flow of oxygen to the sensor).
Heating
At a hot enough temperature the oxygen sensor will produce enough voltage to communicate with the car computer. Typically, the oxygen sensor will include a heating device inside of it. This heating device aids the oxygen sensor by quickly raising the operating temperature (600+ degrees Fahrenheit). Thus a signal to the car computer is produced in a timely manner. Older cars typically have a single lead (wire directly connected to the oxygen sensor) on the oxygen sensor and lack a heating device (operating temperature takes longer to reach). New cars typically possess a self heating oxygen sensor with three or more leads (multiple wires which are directly connected to the oxygen sensor). Over the years, the number of oxygen sensors in any new car has doubled.
Modern Sensor Systems
Modern cars have a second oxygen sensor installed in or behind the catalytic converter. This oxygen sensor monitors converter production. Bigger engines require one oxygen sensor to be installed per cylinder, and an additional oxygen sensor following a catalytic converter. Upstream/ downstream oxygen sensors are installed in many of todays newer cars to monitor emissions performance. This oxygen sensor ensures the converter minimizes pollution (exhaust). Converter failure prompts the malfunction indicator lamp to light up on the dashboard.
Tooling and Wiring
A 22-millimeter socket is used to remove the oxygen sensor from a car. The engine needs to be warmed up just a little bit before removing the oxygen sensor, otherwise the sensor may not budge. The socket is turned counter-clockwise over the bolt holding the sensor in place. Penetrating oil may be used around the bottom of the sensor to help loosen it from its fixture. Wiring on the connector fits all OEM oxygen sensors. Universal oxygen sensors, however, require the wiring connector to be cut. The wires are spliced to connect the connectors wires. Modern sensors typically have four wires (signal, ground, and two wires for the heater circuit. Color coding on a new sensor will not match leads on older converters.
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