NobbyC wrote:

I don't think anything has failed.
The orange low fuel light starts to glow when you have roughly just about 2 gallons and fully illuminates when you are getting close to fumes. 2 gallons left rattling around the tank doesn't give you much range unless your coasting in top gear on a motorway. You don't say what sort of journey you were on - if short and local what sort of mpg do you expect - low teens maybe? As I said your "range" display is based on average readings since the last reset. Yes it should count down to empty i.e. --- but like any simple computer if it doesn't have the right info in the first place the result will not be 100%. For example if you've changed tyre or wheel sizes from factory standard but not put in the changes in the config file then that also alters the way its trying to calculate the variables. I would always consider that the info on MPG etc is about 4% higher than true.
I may be wrong but with so little fuel sloshing about in the tank you could also be at risk of sucking any sediment or even air/vapour into the fuel lines and filter. Honestly, never run it that low cos your tempting fate

Perhaps "glow" was the wrong word to use. What I meant is at about 2.2 gallons the indicator will flicker depending on how the fuel is moving around the tank - i.e. when going up or down hills or side to side around bends. Full permanent Illumination should occur at 2 gallons remaining leaving little margin. I really wouldn't chance running any modern car until the warning light comes on risking running the tank dry as this can cause damage to the fuel pump and engine systems even causing engine misfires and other fuelling issues as well as damage to the cat. Give the old girl a good drink and reset the trip - you may get more reliable readout in future ......... maybe??

Yea I must stress this was the exception not the rule I don’t go that low normally - but my BMW as it is lpg converted and uses very little petrol I only ever have about 40miles in it and been that way for 9 years never an issue ran that right to zero in an emergency still was fine. Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF