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1997 Tahoe 4wd gas gauge sways irratically once down to 1/2

Customer Question

1997 Tahoe 4wd gas gauge sways irratically once down to 1/2 tank. New sending unit installed did not fix problem
Submitted: 8 years ago.
Category: Chevy
Expert:  Carhelp4u replied 8 years ago.

I would first recommend checking the connector that plugs into the fuel pump module on top of the fuel tank. If there are any signs of corrosion, heat, or damaged terminals replace this for sure. Gm has had a real problem with these causing problems with the fuel pump and the fuel level. This system works on a 5 volt reference so you may even want to verify that you do have 5 volts at the black wire as the sensor reference wire, and you may also want to check for erratic readings on the signal wire (purple with white stripe) If this reading is erratic, you may still have a faulty fuel level sensor. From here testing gets tough as we must verify that the signal is getting to the vehicle control module. We must also verify that the connections at the vehicle control module are clean. There is a real good change that this could be a problem with the instrument panel, vehicle control module, or any of the associated wiring, but at this point we need further diagnosis to be certain. If you can do these tests i can further assist you. Here is how this system is wired. Feel free to contact me with any questions or problems and I will further assist you! Good luck!

Object Number: 491401  Size: FS

Carhelp4u and other Chevy Specialists are ready to help you
Customer: replied 8 years ago.
Can you tell me if the VCM also controls any dash lights.
Expert:  Carhelp4u replied 8 years ago.
The check engine light would be controlled by the vcm. This is the only one from what I can see.
Customer: replied 8 years ago.
can u send me a drawing for the vcm