Component description for a hot film mass air flow sensor - GF07.07-P-6000AMG

ENGINE 156.980 in MODEL 164, 251 

ENGINE 156.982 in MODEL 209 

ENGINE 156.983 in MODEL 211, 219 

ENGINE 156.984 in MODEL 216, 221 

Location 

The hot film mass air flow sensors located at the outlet of the respective air filter housing cover.

Task 

The hot film mass air flow sensors (HFM) detect the air mass fed to the engine.

Design 

The hot film mass air flow sensors consist of a temperature regulated resistor and a plastic housing with integrated electronics and a 4-pin plug connector.

Function 

The integral electronics in the hot film MAF sensor controls the nominal temperature (of about 160°C) of the heating resistor. The temperature of the heating resistor is detected via a sensor resistor. If a temperature change occurs as a result of an increased or reduced air flow, the electronics correct the voltage at the heating resistor until the specified temperature is achieved again. This regulating current is evaluated by the hot film MAF sensor and converted into a sensor signal.

The information about air mass is transmitted in the form of frequency and cycle duration of the sensor signal to the ME control unit (N3/10).

Air mass	Frequency	Cycle duration
0 kg/hour	1890 Hz	529 μS
	150 kg/hour	3080 Hz 324 μS
	300 kg/hour	4080 Hz 245 μS
	450 kg/hour	6000 Hz 166 μS
	600 kg/hour	7010 Hz 142 μS

Using STAR DIAGNOSIS, the cycle duration of the sensor signal can be read out.

The intake air temperature of the hot film mass air flow sensor is also detected but not evaluated by the ME control unit. The signal from the intake air temperature sensor (B17) is used for the intake air temperature.