Fuel Gauge shows empty with full tank of gas

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by basic element, Feb 11, 2026 at 6:36 PM.

  1. basic element

    basic element Junior Member

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    I have a 2020 Prius Prime and filled up my gas tank a couple days ago. It rained overnight while I charged the car and this morning, I turned on the car forgetting to unplug the charger. It gave me a warning and so I unplugged it and then noticed the low fuel light was on. When I turned on the car ready to drive, I noticed the fuel indicator had no bars. Totally empty. I thought maybe there was a fuel leak? I took the car to the gas station to fill it up but it only took in .2 gallons before it was full.

    The car drives fine, but the fuel gauge is now broken. I have had rats get into my engine bay so was worried maybe they chewed on some wires? But I don't have any other lights or anything wrong with the car. Anyone else experienced this problem?
     

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    #1 basic element, Feb 11, 2026 at 6:36 PM
  2. PriusCamper

    PriusCamper Senior Member

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    Lol... Your prime went so long without gas it forgot how to measure how much is in the tank. Probably an easy fix by basically doing the equivalent of rebooting your computer. As in disconnect the 12v battery for a few minutes, which will reset the car back to original settings. You'll lose some minor system presets like radio stations and other stuff but it's easy to get that stuff back.
     
    #2 PriusCamper, Feb 11, 2026 at 11:48 PM
  3. BiomedO1

    BiomedO1 Senior Member

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    If you've previously had rat issues - there's a high likelihood that they chewed on your fuel sender wires. If the wires has been chewed, it would most likely be attacked at the fuel pump head. There's also the possibility that the sensor arm or sensor itself is damaged. If you have access to Techstream, you can look at the sensor output directly. Have you tried driving the car in HV mode? You'll need to burn-off some of that gasoline, so it doesn't overflow - if you remove the fuel pump assembly to inspect it.
    You can inspect that area, using the video below.
     
    #3 BiomedO1, Feb 12, 2026 at 12:12 AM
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  4. basic element

    basic element Junior Member

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    I actually fill my tank pretty regularly (once a month) and it actually showed full when it was first filled. It was just the morning I turned on the car and suddenly it showed as totally empty. That's when I decided to go and fill it again and the tank was still full but gauge showed as empty. I did try disconnecting the 12v battery. It reset my clock and calendar but it didn't fix the problem....

    Thanks. I did try driving it in HV mode but maybe it wasn't long enough to burn any significant amount of fuel. I will try it for the next few days. If that doesn't work, I don't have the skills or tools to fix this myself so I will have to take it to a mechanic...
     
    #4 basic element, Feb 12, 2026 at 11:07 AM
  5. BiomedO1

    BiomedO1 Senior Member

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    Just keep the car in HV mode to burn up some of the gasoline; so whomever inspects it - doesn't make a mess....

    Good Luck.....
     
    #5 BiomedO1, Feb 12, 2026 at 1:00 PM
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