Fuel Range On Trip Computer

[SierraOscar]

Hi,

Sorry, this is my first post, and so hopefully I won't make any mistakes

Anyway, I have a 2004 Yaris 1.3 Petrol, and have noticed for the last 6 months, the "Fuel Range" calculator on the Trip Computer no longer works. It stays stuck at 18 miles, despite numerous fills up at the petrol station.

I've tried the reset option (keeping the button pressed in) and I can hear the beep, and that resets the everything apart from the "Range" option. It was working fine since I got the car (2004), and has only started to occur. Rather disconcerting that despite the tank being nearly full it says I have 18 miles to go before it is empty. My understanding was that it did the calculation by taking the current fuel onboard (about 85% full) alongside my average MPG (currently 48mpg) to automatically work this "Range" figure out.

On the main display, I can clearly see the bars on the left showing I have around a 85% full tank.

Anyone have any ideas what I could try?

Many thanks