P0335 - vauxhall corsa c 2001

Question

i have a code p0335 on a odb ii code reader and it says that its the crankshaft positioning sensor cirquit A what does this mean i have replaced the senser just 4 weeks before now the same problem has happenned again but this time the car wont start where as before if the car was cold it would now it wont can someone help by telling what does the circuit A mean is that the sensor or is it the plug or wireing can you help me please