Chapter 3 Automotive Test
59
linear ratio, It needs to be corrected in the ECM; the general output voltage is about 1V at idling speed, and the
voltage rises rapidly during acceleration, reaching a voltage of 4V~4.5V. After stopping the acceleration, it will
return to the idling voltage; the output shows 0V or 5V is not normal.
The digital type has a digital circuit inside the sensor. The output signal is a square wave. The frequency is used to
represent the air flow. A higher frequency means a higher air intake. Use a BNC to banana cable and connect one
end to channel 1 of the oscilloscope. The black plug on the other end is grounded, and the red connector is
connected to the signal wire of the air flow sensor with a needle. Start the vehicle, quickly depress the accelerator
pedal and release it to test, you can view the waveform.
Use the SATO oscilloscope to test the throttle air flowmeter sensor (the air flowmeter is divided into three types:
analog, digital, and hot wire, please test according to different types), the specific operation is shown in Figure 3-
12:
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