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Q: Faulty gas gauge

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The gas gauge on my Buick doesn't work. When the car is off, it goes to E like it should, but when the car is on, the gauge reads full until the car drops under a half or quarter tank, then it drops from full to empty and the low fuel light comes on. Its either full or empty. Also, when i was parked on an incline my tank read about 4/5 full, but then went back to full on level ground. What do you suggest i try? Thanks, -brandon

My car has 206000 miles.
My car has an automatic transmission.

A: The fuel tank sender resistance may be off ...

The fuel tank sender resistance may be off causing either a short or open causing the gauge to either be full or empty. The trunk rear fuel pump access cover should be removed and the connection removed and the fuel sender checked to see if it is between 40 ohms and 250 ohms. If it is, then you have a gauge or wiring connector problem and would need to have the electrical circuit diagnosed and traced to see what is causing it. If the ohms are not as specified then the it has gone bad and the sender should be replaced.

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