Component description for O2 sensor - GF07.04-P-6100AMG
ENGINE 156.980 in MODEL 164, 251
O2 sensors upstream of TWC
ENGINE 156.982 in MODEL 209
O2 sensor upstream of TWC
ENGINE 156.983 in MODEL 211, 219
O2 sensors upstream of TWC
ENGINE 156.984 in MODEL 216, 221
O2 sensors upstream of TWC
Location (wideband oxygen sensor)
The O2 sensors upstream of TWC are bolted into the exhaust pipe upstream of firewall catalytic converter.
Task
The O2 sensors upstream of TWC (control sensors) detect the residual oxygen content in exhaust gas for the following tasks:
- Lambda control
- Self-adjustment of mixture formation
- Function chain tests
Design
The O2 sensors upstream of TWC are insulated as voltage free and designed as a planar (flat) wideband oxygen sensors.
The active sensor ceramic consists of a gas permeable ceramic body made of zirconium dioxide. The inner protective tube with several slots protects the ceramic body from mechanical stresses and from temperature jumps.
The balance resistor (6) is dependent on the overall length (L) and on the type of sensor.
While changing the wideband oxygen sensor, the balance resistor is already fitted on the new sensor and must not be changed (resistance depends on the sensor).
Function (schematic)
The sensor element consists of a combination of a Nernst concentration cell (sensor cell) and an oxygen pump cell which transports (pumps) the oxygen ions.
The pump action is a purely physical process.
When operating in combination with control electronics which are housed in the ME-SFI [ME] control unit N3/10, the wideband oxygen sensor can be measured exactly in a further lambda range (λ 0.7 to 4.0).
Sensor heating
An integrated sensor heater ensures that it remains at the required operating temperature of approx. 750°C. In order achieve the sensor function while the engine is running, wideband oxygen sensors are heated constantly with a heat output of about 10 W.
The sensor heaters are actuated by the ME-SFI [ME] control unit by means of a ground signal.