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

ENGINE 113.967 in MODEL 219 

ENGINE 113.964 in MODEL 164.1 

ENGINE 113.971 in MODEL 251 

Shows model 164.1 

Fig 1: O2 Sensor Heater - Function Diagram

Courtesy 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 through heat control.

The O₂ sensor heater is actuated and pulsed by the ME control unit by means of a ground signal. Each sensor heater has its own, short-circuit proof output stage in the engine control unit with diagnosis. As a protection for the ceramic, the sensor temperature upstream of TWC is limited to approx. 350°C in the condensation phase after cold start. The temperature is then controlled to approx. 700°C after this. The internal resistance of the Nernst cells (which generate the lambda sensor signal) is evaluated. Different values apply to the O₂ sensor heaters downstream of TWC.

Voltage supply to the O₂ sensor heater is fused over the engine circuit 87 relay.

The power absorption capacity of the O₂ sensor heater as of an exhaust gas temperature of 350°C is less than 7 W.

The current in the cold state is increased by the factor 4.