Bosch LSU Planar Wideband Oxygen Sensor

Bosch LSU Planar Wideband Oxygen Sensor: The N62 engine is equipped with new planar wideband oxygen sensors (pre-catalyst). The sensor is planar shaped (type of construction) which is more compact and is made up of thin layers of zirconium dioxide (ZrO2) ceramic films. This modular lamination structure enables the integration of several functions including the heating element which ensures the minimum operating temperature (750 °C) is reached rapidly.

In contrast to conventional oxygen sensors, the wideband features can measure not only at Lambda=1, but also in the rich and extremely lean range (Lambda=0.7 to complete atmospheric oxygen) very rapidly.

To operate effectively, the oxygen sensor requires ambient air as the "reference gas" inside the sensor. The ambient air reaches the inside of the sensor through the plug connection and through the harness. The plug connection socket must therefore be protected from contamination (wax, preservatives, engine degreasers, engine washing, etc.). In the event of the oxygen sensor malfunctioning, the connector should always be checked first with regard to contamination and cleaned if necessary. The plug connection must be disconnected and then reconnected to remove any oxidation from the connector pins.




The pump cell (2) and reference cell (9) are made of zirconium dioxide and each coated with two porous platinum electrodes. They are arranged so that there is a measuring gap (8) of approx. 10 to 50 microns between them. This measuring gap is connected by an inlet opening to the exhaust gas (1). The pump cell is controlled by the ECM applying voltage to the electrodes to initiate oxygen ion pumping across the porous membrane of the reference cell, providing a quicker response time.

If the exhaust gas content is lean, the pump cell pumps oxygen away from the measuring gap to the outside. The direction of flow is reversed for rich exhaust gas content, then oxygen is pumped from the exhaust gas into the measuring gap. The pump current flow is proportional to the oxygen concentration (lean) or the oxygen requirement (rich). The pump is constantly working to maintain that the gas composition in the measuring gap is constantly at Lambda=1. The required current of the pump cell is evaluated by the ECM as a signal that represents oxygen content in the exhaust gas.