Thank you very muchhhhhhhhhhhhhhhhhhhhhhhhhh Pankaj.
Oh my God!!!!I'm really sorry, my mind is in the air!! i'm stupid...
Generally SAP creates a session with the same name as the name of the of the object when you're creating the LSMW, so i almost never check...
and when i made * i didn't find it because SAP creates a weird session this time: ERROR_BALTD that is defined in 13 step as you say, and i didn't pay attention...
SAP is coming up, by default ,with session name "immobilisation" equal to the name of the object, but it should be ERROR_BALTD and not "immobilisation" , and once again, i didn't pay attention 
Thank your very muchhhhhhhhhhh Pankaj