Hiya
DAF CF 65.250, 58 plate 18t Rigid CS
What does this symbol means and why is it on? The regular drivers didn’t know, the truck behaved itself and all went well but it stayed on. It wasn’t red so treated it as an advisory. No manual in the truck either 
Emissions problem, I see it on mine when the Ad Blue gets low. If the Ad Blue is fine then it is a sensor problem, I had it when the Ad Blue tank was full and Daf had to replace something that had become crystallised.
Thanks you Mr Coffeeholic Sah 
Might be an obvious one but I’ve seen this before when another driver started the vehicle up with the exhaust brake stalk in the on position.
Might be worth flicking it a couple of times on and off before you start it up next time and see if it goes off?
As Coffeeholic said though, probably adblue related.
Alex
No smoking in cab…