1999 Tahoe 4 door 4x4 5.7 /auto

In the very back of the gas tank, at the very top of the slope,near the filler/breather: What is that plug in for?

 

On my 97 it was a vent tube, see attched pic

[IMG]local://upfiles/17388/FF9B77C7E62444659B0594A1BF4FE8A0.jpg[/IMG]

 

Heres a pic...

http://i271.photobucket.com/albums/j...gastank002.jpg

 

Its Fuel tank pressue sensor.what it does read below.





The fuel tank pressure (FTP) sensor is a 3 wire strain gauge sensor much like that of the manifold absolute pressure (MAP) sensor, however this sensor has a very different electrical characteristic due to its pressure differential design. The sensor measures the difference between the air pressure, or vacuum in the fuel tank and the outside air pressure.
The sensor mounts at the top of the fuel tank sending unit. A three wire electrical harness connects it to the control module. The control module supplies a 5volt reference voltage and ground to the sensor. The sensor varies a voltage between 0.1-4.9volts. When the air pressure in the fuel tank is equal to the outside air pressure, such as when the fuel fill cap is removed, the output voltage of the sensor will measure 1.3-1.7volts.
When the air pressure in the tank is 4.5inchesHg (1.25kPa), the sensor output voltage should measure 0.3-0.7volts.
The sensor voltage will be approximately 1.5volts when the fuel tank pressure is equalized with ambient pressure. The sensor voltage increases to approximately 4.5volts when a vacuum of 14inchesHg (-3.75kPa) is detected.

 

Would the fuel tank pressure sensor effect the fuel gauge if it is bad or going bad?

 

It should not affect on fuel gauge as it is designed.the fuel level sensor only gives wrong reading,when there is high resistance in ceramic resistor card.

 

Sorry for the late reply.

Thank you for the info on the fuel tank pressue sensor!

I had an issue with my fuel gauge, but resolved it yesterday when I installed a new fuel pump/sending unit, and cleaned up the ground wire.

Thanks again.