Oxygen sensors (or lambda sensors, as they are often known) operate in quite a hostile environment, and are by their nature a limited-life component. They will typically begin to slow down their response or fail completely after around 50,000 - 70,000 miles of normal use, leading to high emissions, poor fuel economy, and often the appearance of the Check Engine Light on the dashboard.

Main dealers tend to charge a premium for replacement sensors, but on a lot of vehicles, the sensors themselves are standard "zirconia" or "planar" type sensors, and are actually compatible with generic replacement sensors known as a "universal" sensors.

In order to make universal sensors fit as many vehicles as possible, they don't come with the connector plug required to plug into the car, as the plugs are different for each vehicle. Instead they have short trailing wires, and you need to cut the wires from your original sensor and crimp or solder them to join to the new sensor, so you re-use your original plug.

To check if your car is compatible with a universal sensor, please see our vehicle application list. If your specific car model is not on that list, please contact us, as not all vehicles are compatible with universal sensors.

Which wire connects to which?

This should be quite simple, but different car manufacturers and sensor manufacturers use a variety of colour schemes for the wires on the sensor, so you may find the wire colours on your new sensor are completely different to the old one, and it's important to connect the wires the right way around.
To do this, it's helpful to understand what each wire does.

The universal sensors we sell have 1, 3 or 4 wires.
- On 1-wire sensors, there is only a single wire to join, so no problem there!
- On 3-wire sensors, 1 wire carries the information from the sensing element. The other 2 wires are either end of a coil, used to heat the sensor up to operating temperature.
- On 4-wire sensors, again 1 wire is the sensor line, and 2 wires are a heater circuit. The additional 4th wire is a ground or earth.

Typically on 3 and 4-wire sensors, the heater wires will both be the same colour.

Colour Scheme Comparisons

3-wire sensors:
The wires on the sensor and the car will most likely each match one of the following two colour schemes. Join the wires to ensure that each wire goes to it's correct counterpart.
The 2 heater wires are just either end of a coil, and so it doesn't matter which way around they are connected.

Wire \ Scheme	1	2
Heater (x2)	Black (2)	White (2)
Sensor	White	Black

We have also encountered some Japanese import vehicles from the early to mid-90's that have a 3-wire sensor made by Bosch Asia, with 1 black, 1 red and 1 white wire. For that specific sensor red & black = heater, white = sensor.

In other cases though, a red or yellow wire usually indicates a titania sensor, which would not be compatible with a universal planar or zirconia sensor.

4-wire sensors:
The wires on the sensor and the car will most likely each match one of the following colour schemes. Join the wires to ensure that each wire goes to it's correct counterpart.
The 2 heater wires are just either end of a coil, and so it doesn't matter which way around they are connected.

Wire \ Scheme	1	2	3	4	5
Heater (x2)	Black (2	Black (2	White (2)	Blue(2)	Brown (2)
Sensor	Blue	White	Black	Black	Purple
Ground	White	Green	Grey	Grey	Tan

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