Sprinter 3500 L5-2.7L DSL Turbo (2004)
Oxygen Sensor: Description and Operation
DESCRIPTION
The wide band oxygen sensor measures the oxygen content in the exhaust gas to control ERG. The sensor is mounted in the exhaust pipe at a 30 degree
angle to prevent the collection of moisture between the sensor housing and element. The sensor is located close to the turbocharger for a quicker
response time.
The oxygen sensor has five wires (heater power and ground, reference voltage, and 2 wires for a pump cell). The oxygen sensor connects to a six wire
harness connector. A non serviceable trimming resistor is built into the sensor connector. The resistance is dependent on the over all length and type of
sensor.
OPERATION
The O2 sensor is a planar zirconium dioxide (Zr02) dual cell limiting current probe with a integral heater. The term wide ban refers to the ability of the
O2 sensor to generate a clear signal over a wide air-fuel ratio measuring range. As a dual sensor, it incorporates a second O2 chamber (oxygen pump
cell), which requires a separate voltage supply.
The sensor element combines a sensor cell (8) and an oxygen pump cell (9). Both cells are made of zirconium-dioxide (Zr02) and a coated with porous
platinum electrodes. The sensor cell operates just like a typical O2 sensor. The oxygen pump cell transport oxygen ions when voltage is applied.
O2 Construction
A gas sample chamber (5) is sandwiched between the oxygen pump cell and the sensor cell. A pump electrode and sensor cell electrode are located in the
sample chamber. A sample passage (10) connects the sample chamber to the surrounding exhaust gas. A sensor cell electrode is located in the reference
air channel (6), which connects to the outside air.
At high temperatures, certain ceramic materials, such as zirconium- dioxide (ZrO2) become oxygen ion conductors. In a typical O2 sensor, the ZrO2 is
used as a solid electrolyte, which contains oxygen ions.
The solid electrolyte is sandwiched between two platinum electrodes. The sensor generates a small voltage when oxygen moves from the high
concentration side to the low concentration side.
