O2 sensor heater, function - GF07.61-P-3025M

ENGINE 275.950 in MODEL 215, 220 

ENGINE 275.951 in MODEL 230 

ENGINE 275.953 in MODEL 216, 221 

ENGINE 275.954 in MODEL 230 

ENGINE 275.980 in MODEL 215, 220 

ENGINE 275.981 in MODEL 230 

ENGINE 275.982 in MODEL 216, 221 

ENGINE 285.950 in MODEL 240 

ENGINE 285.980 in MODEL 240 

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 power.

The O₂ sensor heater is pulsed (actuated) by the ME-SFI [ME] control unit via a ground signal. The output of the O₂ sensor heater 2 at operating temperature is about 7 W.

Power supply to the O₂ sensor heater occurs for:

• Model 215, 220 from the right front fuse and relay module
• Model 230 from the passenger-side fuse and relay module
• Model 240 from the driver-side SAM control unit with fuse and relay module
• Model 216, 221 from the front SAM control unit with fuse and relay module

In the cold state, the current is increased approximately by a factor of 4. At coolant temperatures under about 20°C and for high engine speeds the O₂ sensor heater is switched off.

Every O₂ sensor heater has its own, short circuit proof, output stage which can be diagnosed in the ME-SFI [ME] control unit. As a protection for the ceramic, the O₂ sensor temperature upstream of TWC is limited to approx. 350°C in the condensation phase after the cold start. After this, the temperature is controlled to approx. 700°C. To do this an exhaust temperature is determined from various engine operating data and appropriate heating takes via the O₂ sensor heater.

Different values apply to the O₂ sensor heaters downstream of TWC.

	ME-SFI [ME] control unit, location/task/design/function		GF07.61-P-5000M
	O2 sensors, location/task/design/function		GF07.04-P-4103M
	Crankshaft position sensor, location/task/design/function		GF07.04-P-4116M
	Coolant temperature sensor, location/task/design/function		GF07.04-P-5026M