Was given a sensor and told to find out what it was and how it worked. After some failed research online all I had was that it was some kind of pressure sensor. Luckily, one of the engines at school had the same sensor on the EGR system. Jeff informed me that it was a differential pressure sensor. It is placed after the EGR cooler and before it is mixed with the intake air. The sensor is placed on a venturi and reads the pressure before and after it. From this reading the ECM can calculate the flow rate and then know what the fuel/air mixture should be. This is a three wire sensor, meaning it has a 5v supply, signal, and ground wire. I hooked up a multi-meter to it as well as a 5v supply and then grounded it. The sensor is pretty sensitive and you can see the voltage fluctuate by blowing in one end at a time.
On the left you can see the voltage increasing and on the right you can see the voltage decreasing. Just from a light blow of air on either side could make this sensor work.
After working the sensor I opened it up to take a look at the inside of the sensor. The small board inside was attached to a drum like sensor that would cause voltage flow to increase or decrease depending on which side you applied pressure to.
Applying very light pressure with my finger you can see the reading on the right dropped drastically, light pressure on the other side caused the reading to increase. 
Hours 36
Running Total for Fall Qtr: 264
I thought that this was a cool one...thanks for doing that.
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