GF07.07-D-6000HD | Component description for hot film mass air flow sensor | 22.6.11 |
ENGINES 651.955 /956 /957 in MODEL 906
ENGINES 651.940 in MODEL 639.6 /70
with CODE (XZ1) Model generation 1
with CODE (MZ0) BlueEFFICIENCY
D07.04-1180-05
Location
Shown on engine 651.955
B2/12 Hot film mass air flow sensor
B2/12b1 Intake air temperature sensor
The intake air temperature sensor (for model 906) or intake air temperature sensor (B2/8b1) (for model 639) is located in the housing for the hot film MAF sensor.
Task
- Monitoring the aspirated air mass
- Detection of the intake air temperature by the intake air temperature sensor
Input and output signals
Direct input signals
- Supply voltage for the CDI control unit (N3/28)
Direct output signals
- Analogous frequency open collector output to determine the suctioned in air mass at the CDI control unit
- Analogous voltage output to determine the intake air temperature at the CDI control unit
Function
2 temperature-dependent resistors (air temperature and current sensor) lie in the air intake stream of the hot film MAF sensor. By changing the air mass flow the flow sensor is cooled more or less strongly. The electronics in the hot film MAF sensor sensor module regulates the heating current through the flow sensor at a constant temperature which is above the intake air temperature. This heating current is converted into a frequency analogue signal. This frequency serves the CDI control unit as information about the air mass. The intake air temperature is determined over the separate intake air temperature sensor with a resistor with negative temperature coefficients (NTC). The change in voltage is converted in combination with a pull-up resistor (voltage divider) in the CDI control unit into a voltage analogue signal and is available as information about the intake air temperature.