I am trying to reverse engineer a pressure sensor thats connected to an ECM and outputs pressure ratings in bars.
i want to tap into the sensor with arduino and create my own voltage --> bars data.
This is the sensor wiring diagram, the sensor is "G31"
from my research, i am concluding that pin 3 is the Ref voltage from ECM, which is tied into another sensor (idk why). pin 1 is ground and pin 4 is signal.
i tested all 3 pins WRT to a known ground, while disconnected from the sensor but connected to ECM and power on.
pin 1: 0v
pin 2: does not exsist.
pin 3: 5.5v (ref)
pin 4: 4.95v (signal).
when i logged pin 4 voltage WRT to ground, and callaborated that data to the known pressure, i got a graph that does not represent any function, it was literally a square blob of data.
2 possibilities for this:
1: Pin 1 (ground) floats, need to tap into ECM ground.
2: Reference voltage changes, need to log voltage drop WRT to ref.
do those 2 options make sense, and which would be most likely?