Very Quick Guide to Lambda Sensors

A lambda sensor is an electronic oxygen sensor that fits into the exhaust system. Its purpose is to send a voltage signal to the ECU to indicate how much oxygen is in the exhaust gases. This in turn indicates how efficiently the engine is running. The ECU uses this information to continually adjust the engine's fuelling requirements.

What happens if it fails?

MOT emissions failure, excessive fuel consumption, catalyst failure, poor performance, engine check warning light, fault codes are all symptoms that can be associated with Lambda sensor failure. The Lambda sensor has a limited service life and its operation deteriorates over a period of time.

Maintenance

No maintenance of the Lambda sensor is required and there are no internally serviceable parts. Should the sensor's operation deteriorate then it should be considered to have reached the end of its serviceable life, cleaning the sensor will not rejuvenate it. It is important that the engine management system and the vehicle's emissions be regularly serviced and checked.

Where is it?

Mounted in the exhaust system manifold or front pipe. Most modern engines with a close-coupled catalyst have the sensor inside the engine compartment. It can be either at the front or back of the engine, depending on the location of the exhaust manifold. On older cars it can also be halfway down the front downpipe or immediately in front of the catalyst when sited underneath the car.

Newer cars have multiple sensors for each Bank of cylinders, or pair of cylinders. Cars made after year 2000 have at least two sensors, front and rear, and are termed "OBDII compliant", and meet Euro 3 emissions regulations, sometimes termed "euro 2000". Multiple sensors enable the ECU to better judge the efficiency of individual cylinder pairs.

How can I replace it?

Consult our fitting guide - it's roughly the same as fitting spark plugs. Or get your garage to do it. We can supply sensors for a wide range of vehicles and ship to the UK mail order and across the world too.

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