Switches & Sensors
5 Wire Lambda Sensor Technology
Since the introduction of Euro 4 emissions standards*, the 5-wire Lambda sensor has become an essential component in modern lean burn and direct injection engines. Traditionally, the signal sent from the Lambda sensor to the ECU was a binary signal, indicating that the air-fuel mixture was either rich or lean. The binary sensor (or narrowband sensor) only operates within these two extremes; it cannot tell the ECU to what degree the mixture is rich or lean.
Beyond the basics
The 5-wire sensor sends a more sophisticated message to the ECU. The signal is no longer simply rich or lean; it is a constant and variable voltage from 0 to 5 volts (with 0 indicating an extremely lean mixture and 5 volts indicating a very rich mixture). This helps the engine to maintain a stoichiometric** air-fuel mixture because the ECU can adjust fuel injection according to these measurements provided by the Lambda sensor.
Why do the wires matter?
• 1st wire = signal voltage
• 2nd wire = isolates the ground of the signal to reduce signal noise
• 3rd and 4th wires = heating element so the sensor starts operating faster and more reliably***
• 5th wire = detects by how much the air-fuel ratio is too rich or lean
5-wire (or wideband) and air-fuel ratio sensors (also known as AFR or lean burn sensors) are now available in the Cambiare range which is listed on MAM Autocat, Epicor Mastercat and Cambiare’s own online catalogue which can be accessed free of charge at www.cambiare-ve.com
Cambiare 5-wire Lamda sensors cover popular applications, including:
* Euro 4 applies to new model types approved on or after 1st January 2005 and became applicable to all models from 1st January 2007
** stoichiometric = the point at which the air-to-fuel ratio gives complete combustion (14.7 parts air to 1 part fuel)
*** narrowband sensors have an operating temperature in the region of 316°C. The 5-wire sensor operates in the range of 632°C to 815°C