It is an electronic device that measures the proportion of oxygen (O 2) in the gas or liquid being analysed.
The lambda sensor measures the amount of unburned oxygen in the engine exhaust. It then sends a signal to the ECU, which adjusts the fuel & air mixture for optimum engine performance. The lambda sensor is important in controlling exhaust emissions. Common symptoms of lambda sensor failure include excessive fuel consumption, engine surges or stuttering, and the engine management light illuminating. Failure will also result in high hydrocarbon emissions, causing failure at an emissions check (part of the MOT process). Best Answer: No it will still start fine. All the Lambda Sensor does is send signals to the computer so that the engine can run a leaner mixture once the car has warmed up. You will definitely lose some economy having a faulty one. At worst you could also damage the Catalytic Converter. The car will run the same with a faulty one.  What is an Oxygen Sensor? The oxygen sensor, also known as a lambda sensor, was developed in the late 1960s by Dr. Gunter Bauman for the Robert Bosch GmbH company. This sensor is an electronic device used to measure the proportional amount of oxygen in a liquid or gas.  The precise control required to operate this system is provided by the use of an exhaust gas oxygen (Lambda) sensor installed upstream of the catalyst. A Lambda sensor has the ability to precisely measure the air/fuel ratio present in exhaust gases. By sending a signal to the control unit it can initiate a change to keep the fuelling system operating within the very tight tolerances required. This is known as a closed-loop control system.  1 Lambda denotes the oxygen sensor in a vehicle that measures the air-to-fuel ratio in the exhaust gases of an internal-combustion engine. 2  A Lambda 4S solid-fuel rocket was used to launch Japan's first orbital satellite in 1970.  Technical information. The lambda sensor is also referred to as the Oxygen O 2 sensor or a Heated Exhaust Gas Oxygen (HEGO) sensor and plays a very important role in control of exhaust emissions on a catalytic equipped vehicle. Waveform notes. The lambda sensor is also referred to as the Oxygen (O 2) sensor 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. The sensor will have 4 electrical connections and it reacts to the oxygen content in the exhaust system and will produce an oscillating voltage between 0.5 volt (lean) to 4.0 volts, or above (rich) when running correctly An oxygen sensor (or lambda sensor) is an electronic device that measures the proportion of oxygen (O 2) in the gas or liquid being analysed. It was developed by the Robert Bosch GmbH company during the late 1960s under the supervision of Dr. Guenter Günter. bauman Since oxygen sensors are located in the exhaust stream, they do not directly measure the air or the fuel entering the engine but when information from oxygen sensors is coupled with information from other sources, it can be used to indirectly determine the air-fuel ratio. The Oxygen Sensor (OS), which is also commonly know as a Lambda Sensor [Figure 1], is a ceramic device placed in the exhaust manifold [Figure 4] on the engine side of the catalytic converter (CAT). Any car which is injection fuelled and has a CAT, will need a OS fitted to function properly. 
http://www.sensors.uk.com/Lambda-Sensor.html https://uk.answers.yahoo.com/question/index?qid=20110724114110AAIcrKM http://www.meineke.com/blog/oxygen-sensor/ http://www.ngkntk.co.uk/index.php/technical-centre/lambda-sensors/what-does-the-lambda-sensor-do/ https://en.wikipedia.org/wiki/Lambda https://www.picoauto.com/library/automotive-guided-tests/titania-lambda-sensor https://en.wikipedia.org/wiki/Oxygen_sensor http://www.topbuzz.co.uk/info/oxygen_sensor/oxygen_sensor.htm
what does a lambda sensor do