Mass air flow sensor (686), EDC16
| Mass air flow sensor (686), EDC16 |
| Location |
Mass air flow sensor (686)
| Main task |
Measures the air flow to the engine and the air temperature.
| Type |
The air temperature is measured with an NTC resistor.
Technical data .
| Connection, mass air flow sensor 205 |
Common power supply via pin 1 and 2.
| Pin no. | Signal type | Description |
|
1
|
Power supply
|
Connected to fuse 27 on the instrument panel fuse board.
|
|
2
|
Ground
|
Connected to ECM pin 44(A).
|
|
4
|
Variable frequency
|
Connected to ECM pin 42(A).
|
| Connection, temperature sensor 772 |
Common power supply via pin 1 and 2.
| Pin no. | Signal type | Description |
|
1
|
Power supply
|
Connected to fuse 27 on the instrument panel fuse board.
|
|
2
|
Ground
|
Connected to ECM pin 44(A).
|
|
3
|
PWM
|
Connected to ECM pin 37(A).
|
| Function, mass air flow sensor 205 |
A module is located in the centre of the air duct. A small amount of the intake air passes via a duct and silicone film, which measures the flow and direction of flow.
A network of temperature sensitive resistors and a heating resistor are etched on the film. The heating resistor is located in the centre of the film along with a temperature sensor that controls heating. The resistive sensors are located symmetrically on either side of the heating zone. If no air passes over the film, the drop in temperature from the centre of the film to the edges is linear and the pairs of resistive sensors show the same temperature. When air passes over the film, the leading edge and the resistive sensors that the air meets first are cooled. The resistors on the other side of the heating zone maintain virtually the same temperature since the air is heated as it passes over the film. The difference in resistance is compared to the reading from the temperature sensor in the centre zone by a signal amplifier and signal processor. In this way, the mass air flow sensor can determine the size and direction of the air flow.
The output signal is a frequency that is a function of the magnitude of the air flow. Since the frequency is not crystal controlled, this frequency can be used as a guiding value for the deviation from the nominal frequency for a certain air flow.
| Function, temperature sensor 772 |
The temperature is measured with an NTC resistor. The value is converted to a PWM signal. The frequency is not crystal controlled and can be used to compensate the frequency deviation of the mass air flow sensor.
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