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Experts in car diagnostics since 2001
  Home Articles Oxygen (Lambda) sensors

Quick guide to Oxygen (Lambda) sensors

What is a Lambda sensor?
How can I tell if it needs replacing?
Where will I find the Lambda sensor?
Which type do I need?
How do I change the sensor?
Where can I buy a replacement sensor?
Is it safe to use a non-original sensor in my car?

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).
There are exceptions! Japanese vehicles will often have blue and green wires amongst their wire colours - Japanese vehicles tend to have Zirconia sensors. The Toyota Carina E vehicles are unique - they use a special rapid heating 'lean burn' sensor to cope with Toyota's highly fuel-efficient Lean Burn engine.

NOTE: Universal Zirconia sensors are not suitable for Rover vehicles with MEMS engine management systems and Toyota Carina E cars (and other Toyota vehicles using the same engine/control system).

How do I change the sensor?
Direct-fit sensors are supplied with the electrical connecting plug for your specific vehicle. The old sensor can be removed and simply swapped with the new one.

Universal sensors are supplied without the connecting plug. The plug from the sensor on the car will need to be transferred to the new sensor (this can be soldered or crimped using the crimping bullets supplied).

All of our sensors come with complete fitting instructions.

Where can I buy a replacement sensor?
We currently stock a range of direct replacement sensors (please see our Direct-fit Application List). We also stock Universal Zirconia sensors with one, three or four wires. If we don't stock the sensor you require, we can usually order one in for you within a couple of days.

Is it safe to use a non-original sensor in my car?
Yes. Our Lambda Sensors:
  • are made to O.E. standards and usually by the same manufacturer
  • are manufactured to the highest quality and are all factory pre-tested
  • are 100% heat and pressure tested to assure performance under the most demanding conditions
  • have threads which are coated with high temperature anti-seize grease
  • carry a 12 month warranty
It is very unusual to come across a genuinely faulty sensor. When faults are reported, the most common cause is incorrect fitting of the sensor.
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