Lambda Sensor - Zirconia The lambda sensor is also referred to as the Oxygen O2 sensor or a Heated Exhaust Gas Oxygen (HEGO) sensor and plays a very important role in the control of exhaust emissions on a catalytic equipped vehicle. The lambda sensor is fitted into the exhaust pipe before the catalytic converter; cars using the new EOBD2 will also have a post cat lambda sensor.
The sensor will have varying electrical connections and may have up to four wires; it reacts to the oxygen content in the exhaust system and will produce a small voltage depending on the Air/Fuel mixture seen at the time. The voltage range seen will, in most cases, vary between 0.2 and 0.8 volts: 0.2 volts indicates a lean mixture and a voltage of 0.8v shows a richer mixture. A vehicle equipped with a lambda sensor is said to have 'closed-loop', this means that after the fuel has been burnt during the combustion process, the sensor will analyze the resultant emissions and readjust the engine's fuelling accordingly. Lambda sensors can have a heater element which heats the sensor to its optimum operating temperature of 600℃, this enables the sensor to be located further away from the heat source at the manifold to a 'cleaner' location.
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