Hot film MAF sensor, component description - GF07.07-P-6000V
ENGINE 272.920 in MODEL 203 up to Model Year 8
ENGINE 272.922 in MODEL 211
ENGINE 272.940 in MODEL 203 up to Model Year 8
ENGINE 272.941 in MODEL 203 up to Model Year 8
ENGINE 272.942 in MODEL 171 up to Model Year 8
ENGINE 272.943 in MODEL 211, 219
ENGINE 272.944 in MODEL 211
ENGINE 272.945 in MODEL 251 up to Model Year 8
ENGINE 272.946 in MODEL 221 up to Model Year 8
ENGINE 272.960 in MODEL 203 up to Model Year 8
ENGINE 272.963 in MODEL 171 up to Model Year 8
ENGINE 272.964 in MODEL 211, 219
ENGINE 272.965 in MODEL 221 up to Model Year 8
ENGINE 272.966 in MODEL 230 up to Model Year 8
ENGINE 272.967 in MODEL 164, 251 up to Model Year 8
ENGINE 272.970 in MODEL 203 up to Model Year 8
ENGINE 272.972 in MODEL 211
ENGINE 272.975 in MODEL 221 up to Model Year 8
ENGINE 272.985 in MODEL 211, 219
ENGINE 273.922 in MODEL 221 up to Model Year 8
ENGINE 273.923 in MODEL 164 up to Model Year 8
ENGINE 273.924 in MODEL 221 up to Model Year 8
ENGINE 273.960 in MODEL 211, 219
ENGINE 273.961 in MODEL 216, 221 up to Model Year 8
ENGINE 273.962 in MODEL 211
ENGINE 273.963 in MODEL 164, 251 up to Model Year 8
ENGINE 273.965 in MODEL 230 up to Model Year 8
ENGINE 273.967 in MODEL 209
ENGINE 273.968 in MODEL 221 up to Model Year 8
ENGINE 272.940 in MODEL 209
ENGINE 272.960 in MODEL 209
Location
The hot film mass air flow sensor is located behind the intake manifold between the air filter housing and the throttle valve actuator.
Task
The hot film MAF sensor detects the air mass supplied to the engine and the intake air temperature.
Design
A temperature-controlled resistor detects the air mass and an integral NTC resistor detects the intake air temperature.
The flow to the hot film sensors is even through the grid. The hot film MAF sensor has an oval housing and 4-pin (production start) or 5-pin plug connector.
The electronics and the housing have undergone a number of modifications (please note part number!).
Function
The electronic control in hot film mass air flow sensor controls the temperature of the heating resistor (R H ) by means of a variable voltage, so that its temperature is 160°C above the intake air temperature detected by the temperature resistor (R L ).
The temperature of the heating resistor (R H ) is detected by the sensor resistor (R S ). If a temperature change occurs as a result of an increased or reduced air flow, the electronics adapts the voltage at the heating resistor (R H ) until the temperature difference is again achieved.
This control voltage is used by the engine control unit as a measure for the metered air mass. The air mass is transmitted via a frequency signal (low frequency for low air mass) to the ME control unit. Using STAR DIAGNOSIS, the cycle duration of the frequency signal can be read out in seconds.
The intake air temperature is detected by an additional NTC resistor.
Examples:
| Air mass | Frequency | Cycle duration | Intake air temperature | Resistor |
|---|---|---|---|---|
| 0 kg/h | 1890 Hz | 529 μS | -40°C | 39 k Ω ±5 % |
| 150 kg/h | 3080 Hz | 324 μS | 0°C | 5.5 k Ω ±5 % |
| 300 kg/h | 4080 Hz | 245 μS | +40°C | 1.1 kΩ ±5 % |
| 450 kg/h | 6000 Hz | 166 μS | +100°C | 0.2 kΩ ±5 % |
| 600 kg/h | 7010 Hz | 142 μS |
Hot film MAF sensors with the number A 273 094 08 48 and higher provide the engine control unit with an additional signal at a frequency ranging between 17 and 21 Hz (44 to 54 ms). With this so-called ratio-metric frequency signal, the engine control unit compensates for the temperature and voltage influences at the air mass signal.
The engine control unit also detects the version of the hot film MAF sensor via the duty cycle.