jv_auto_service

i have change the plug on the auto transmision box as it had a leak, also replaced gaket on gerabox sump, since putting the aft fluid the dealer recomended it has fetched engine managment light on and will not change out of first gear?? am i right to believe this is limp mode?? does any1 have any help on how i can put this right?? or come accross this problem, just from the plug been unplugged from auto gearbox sump??