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O2 sensor heater function - GF07.61-P-3025V

ENGINE 272.920 in MODEL 203 

ENGINE 272.922 in MODEL 211 

ENGINE 272.940 in MODEL 203, 209 

ENGINE 272.941 in MODEL 203 

ENGINE 272.942 in MODEL 171 

ENGINE 272.943 in MODEL 211 

ENGINE 272.944 in MODEL 211 

ENGINE 272.945 in MODEL 251 

ENGINE 272.946 in MODEL 221 

ENGINE 272.960 in MODEL 203, 209 

ENGINE 272.963 in MODEL 171 

ENGINE 272.964 in MODEL 211, 219 

ENGINE 272.965 in MODEL 221 

ENGINE 272.966 in MODEL 230 

ENGINE 272.967 in MODEL 164, 251 

ENGINE 272.970 in MODEL 203 

ENGINE 272.972 in MODEL 211 

ENGINE 272.975 in MODEL 221 

ENGINE 273.922 in MODEL 221 

ENGINE 273.923 in MODEL 164 

ENGINE 273.924 in MODEL 221 

ENGINE 273.943 in MODEL 164 

ENGINE 273.960 in MODEL 211, 219 

ENGINE 273.961 in MODEL 216, 221 

ENGINE 273.962 in MODEL 211 

ENGINE 273.963 in MODEL 164, 251 

ENGINE 273.965 in MODEL 230 

ENGINE 273.967 in MODEL 209 

ENGINE 273.968 in MODEL 221 

Shown on engine 272.963 in model 171 

Fig 1: O2 Sensor Heater Function (Shown On Engine 272.963 In Model 171)
G04738381Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The purpose of the O2 sensor heater is to rapidly heat up the O2 sensors to their operating temperature while preventing damage to the sensor ceramic as a result of controlled heating.

O 2  sensor downstream TWC (Lambda discrete sensor) 

The sensor heater of the O2 sensors downstream of TWC is actuated via GND and pulsed by the ME control unit. The mean pulsed heating current is approx. 400 mA in idle speed range. The current in the cold state is increased approximately by the factor 4.

The sensor heater is switched off at coolant temperatures below approx. 20°C and at high engine speeds as a protection for the sensor ceramic.

O 2  sensor upstream of TWC (broadband oxygen sensor) 

The O2 sensors upstream of TWC are heated continuously during engine operation, to guarantee their function.

Temperature control and temperature measurement (by means of an internal resistance measurement) are performed by the ME control unit by means of a special internal control electronics.

Voltage supply to the sensor heater takes place fused over the relay for circuit 87. Every sensor heater has its own short-circuit-proof output stage with diagnosis switching to ground in the engine control unit.

  Component description for the ME-SFI [ME] control unit   GF07.61-P-6000V 
  Component description for the coolant temperature sensor   GF07.04-P-6040V
  Component description for the crankshaft Hall sensor   GF07.04-P-6220V
  Component description for an O2 sensor O2 sensors upstream of TWC GF07.04-P-6100V
    O2 sensors downstream of TWC GF07.04-P-6100VA
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