Component description for the hot film mass air flow sensor - GF07.07-P-6000CY

ENGINE 272.911 in MODEL 204.0 up to Model Year 8

ENGINE 272.921 in MODEL 204.0 /2 up to Model Year 8

ENGINE 272.947 in MODEL 204.0 /2 up to Model Year 8

ENGINE 272.948 in MODEL 204.0 up to Model Year 8

ENGINE 272.961 in MODEL 204.0 /2 up to Model Year 8

ENGINE 272.971 in MODEL 204.0 up to Model Year 8

Location

The hot film mass air flow sensor is located behind the variable intake manifold between the air filter housing and the throttle valve positioner (M16/6).

Fig 1: Identifying Hot Film Mass Air Flow Sensor

Courtesy of MERCEDES-BENZ USA

Task

The hot film MAF sensor detects the air mass sent to the engine and the intake air temperature and sends an appropriate voltage signal to the ME-SFI [ME] control unit (N3/10).

Design

The intake air temperature is also detected by one further temperature resistance.

The electronics and the housing have undergone a number of modifications (please note part number!).

Fig 2: Identifying Hot Film Sensor And Electronics Housing

Courtesy of MERCEDES-BENZ USA

Function

Electronics in the hot film mass air flow sensor regulate via a changeable voltage the temperature of the heating resistor (RH) in such a way, that its temperature lies 160°C above the intake air temperature detected by the temperature resistor (RL).

The temperature of the heating resistor (RH) is detected by the sensor resistor (RS). For temperature changes due to an increased or reduced rate of air flow, the electronics readjust the voltage at the heating resistor (RH), until the temperature difference is reached again 160°C.

The ME-SFI [ME] control unit uses this control voltage as a measurement of the air mass supplied.

The air mass is transmitted via a frequency signal (low frequency for low air mass) to the ME-SFI [ME] control unit. Using DAS, the cycle duration of the frequency signal can be read out in "μ seconds".

The intake air temperature is detected by the integral intake air temperature sensor (B2/5b1) in the hot film mass air flow sensor.

Hot film mass air flow sensors with the number A 273 094 08 48 and higher transmit an additional signal to the ME-SFI [ME] control unit. With this so-called ratio-metric frequency signal, the ME-SFI [ME] control unit compensates for temperature and voltage influences on the air mass signal.

The ME-SFI [ME] control unit also detects the version of the hot film MAF sensor via the duty cycle.