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Test any 3 wire pressure sensor
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Here is the procedure to test any 3 wire pressure sensor
First find out pinout for sensor. On most sensors when you look at the base of the sensor
connector you can find description for the wires. GND –> ground. V –> (+) 5v voltage from ECU
O –> Voltage output from sensor (+). If you are unsure of the pinout on the sensor you can check
The connector on the car side like this: Remove sensor, turn the ignition on, and do not start the car!
Connect negative voltmeter probe somewhere on the car ground. With positive probe pouch each
Pin on the car side connector. If the voltage on the pin is 0v than that pin is ground.
If the voltage on the pin is 5v or 4.99v than that pin is the voltage input from the ECU.
If the voltage on the pin is somewhere in between 6v and 8v then that pin is the voltage output from the sensor.

Now you have the correct pinout from the senor and we can test it on the bench.
I have used 3x AAA 1.5 volts battery, connect them in series to get the 4.5V needed to drive the
sensor. Connect as described in the schematic.     Then apply some air pressure. I have used syringe
Because it was laying around. You can use your mouth or foot pump also.
The voltmeter is showing 1.88v, when you release pressure the voltage will raise.    
Important is that voltage raise or voltage drop is without “hops“, steady and linear corresponding
With air pressure. Of course you don’t have to worry what exact air pressure equals with amount of voltage
This test I have made because Lexia had throve me an error pressure sensor open loop or shortcut to earth.
So I had to test the sensor. Finally it turned out that wire loom had a bad earth connection.
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