The yellow injection system warning light came on my Multijet diesel when my diesel had was almost empty, first time I've seen the light come on and first time I've allowed the diesel to go so low, I usually fill up once it reaches a quarter of a tank. I've popped almost a tank in and it's gone off and been off for over 24 hours now. Do I still need to get this checked or was it because I had let it go too low?

Thanks in advance for all advice

Just wanted to mention if you don't get as many replies or the info you need for peace of mind on here give your local Fiat dealer a call and ask for servicing. Maybe the two nearest to you for a balanced opinion. They might be able to shed light on the matter from past experiences with other customers and rule out any known problems? best of luck

Not a problem to worry about. There may be a stored fault code as a result, and it would be sensible to have this read by a scanner, noted, and then cleared.
The time to take further action would be if it returns after clearing.

Just a general note: When clearing codes, always make a note of them first. It builds a history of the vehicle and is useful if future problems arise.

If it was the fuel system warning, not just the low fuel level, it was probably water in the fuel. The filter probably has a sensor. Having topped it up, the water is better diluted, but will still be there. This occurs naturally.

Read the handbook about draining the water out of your filter, and do it regularly.

Air contains moisture. Any air in the fuel tank overnight can lead to this moisture condensing, and it naturally goes to the bottom, as the fuel sits on top. This is why many lorries and buses keep the tank full overnight. Less air!