Component description for an oxygen sensor - GF07.04-P-6101CY

ENGINE 272.911 in MODEL 204.0 up to Model Year 8 Oxygen sensor before catalytic converter

ENGINE 272.921 in MODEL 204.0 /2 up to Model Year 8 Oxygen sensor before catalytic converter

ENGINE 272.947 in MODEL 204.0 /2 up to Model Year 8 Oxygen sensor before catalytic converter

ENGINE 272.948 in MODEL 204.0 up to Model Year 8 Oxygen sensor before catalytic converter

ENGINE 272.961 in MODEL 204.0 /2 up to Model Year 8 Oxygen sensor before catalytic converter

ENGINE 272.971 in MODEL 204.0 up to Model Year 8 Oxygen sensor before catalytic converter

Location

Oxygen sensors upstream of catalytic converter (KAT) are screwed into the exhaust pipe upstream of the firewall catalytic converter.

Fig 1: Identifying Oxygen Sensor Components Location

Courtesy of MERCEDES-BENZ USA

Task

Oxygen 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 test (for OBD II or EOBD)

Design

The oxygen sensors upstream of TWC are insulated as voltage free and designed 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.

Fig 2: Identifying Oxygen Sensor Design

Courtesy of MERCEDES-BENZ USA

Fig 3: Identifying Oxygen Sensor Overall Length

Courtesy of MERCEDES-BENZ USA

The balance resistor (6) is dependent on the overall length (L) and on the type of sensor.

While changing a 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)

Fig 4: Identifying Oxygen Sensor Function Schematic

Courtesy of MERCEDES-BENZ USA

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

The 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.