abiec

i got a 2000 model a4 avante with a 5hp19 box in it the box keeps on going into limp mode with a fault code turbine speed sensor implausible i have checked the wiring and put a new sensor in still the same. when i got the car i did not have any history about it. upon futher queries with the previous owner he said that he did change the box and from then the problems started for 8 months he battled and no joy. now according to zf there are 2 5hp19 boxes that was put into the audis one with a magnetic turbine speed sensor and one with a hall type speed sensor. i cant find anyone that can give me info or point me in the right direction. can anyone help me please