2000 w202 starting problem

[fdmk2]

i have a 2000 w202 c220 cdi which has stopped starting,ignition comes on and steering lock disengages so im assuming key system is ok,but when key is turned to start position nothing happens,i have lives and earths at computer and also the igniton live,i think it might be problem from auto gearbox module which i found got wet,is it possible to change this from an identicle vehicle or is it coded.