What is a Lambda sensor?
A Lambda or Oxygen sensor measures the amount of oxygen in the exhaust system. It sends signals to the on board computer which adjusts the air/fuel ratio to the correct mixture.
How can I tell if it needs replacing?
Lambda sensor failure may be indicated by increased fuel consumption, an increase in emissions, CAT failure or possibly the illumination of a 'check engine' light.
Lambda sensors should be replaced according to the vehicle manufacturer's guidelines. In general, sensors should be checked every 25,000 to 30,000 miles and renewed every 60,000 to 80,000 miles.
Where will I find the Lambda sensor?
Mounted in the exhaust system manifold or front pipe, as close to the engine as possible (it resembles a small spark plug). Year 2000 on vehicles may have two sensors, one before and one after the catalytic converter. 'V' configuration engines may also have one sensor per bank.
Which type do I need?
To help identify which sensor you need:
Count the Wires
Your sensor may have between one and seven wires - three and four wire sensors are the most common.
Check the Colour of the Wires
There are two basic types of Lambda sensor - Zirconia and Titania. The colour of the wires helps to identify which type you have.
Zirconia sensors are fitted to 90% of vehicles in the UK fitted with a catalytic converter - the sensor will usually have black, grey, purple or white wires (or a combination of these).
Titania sensors are far less common - such a sensor will have a red wire, a yellow or both fitted to it (most commonly found on late Vauxhall Ecotec engines, late BMW, Range Rover and some early Rover 800
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