Peugeot FAP fluid low warning l,do you have to fill it full?

[robbocop33]

Just had the low dpf fluid warning pop up this morning on my 2009 peugeot 407 diesel.
Diagnistic tool backs this up and tells me there's 23 fl.oz in it.
Question is,is it a case of just putting in enough to keep the level sensor happy then i just reset the warning sensor with my scan tool,or do you have to fill it right up?
Thanks!!

[stevemcs]

They usually take between 1 and 3 litres and you really should fill it, some recognise the top up, some don't. Some also have a bag that you have to replace

[robbocop33]

Thanks!