fuel gauge issue

When I topped off once it took a couple of starts to have the gauge show full. It can also take some distance for the gauge to show full on a normal fill of 6-8 gallons. IMO no need to worry. As you continue to drive does it eventually register full or does the next pip disappear?

 

Just filled mine tonight and noticed the same phenomenon, but as I drove away, it slowly migrated up to full scale - took about 2 minutes.

I suspect it takes time for the levels in the tank and the secondary reservor to equalize.

 

Might be a problem with the floater or the sensor?

 

Maybe refueling will help.

The systems probably differ enough to make my 2002 Audi A4 experience irrelevant to your Prius, but just for entertainment: here is the story.

I left a thermoelectric cooler rated at 4.5 Amps plugged into the cig lighter accidentally. Two hours later the 6-year old OEM battery was depleted enough that the cabin lights came on dim and when I (foolishly) tried to start the car the engine would not turn over. I saw the 12V line dip below 7V on my ScanGuageII readout, and as it only samples once per second and I was not watching continuously I don't know the real low.

After I recharged the battery everything work fine, except that a few remembered entries were gone, and the gas gauge read zero. Not low, zero. The tank was actually about full, so I drove it long enough to be able to put in three or four gallons. For the next half hour of driving the indicated level steadily rose, finishing at about right.

Oh yes, I did replace the 12V battery before winter came.

It is worth remembering that even the dial gauges on modern cars are often just computer readouts, and if one feeds the computer an unexpected sequence of events, it may provide an absurd output.