B5 1.8t Crank speed sensor?

[DragonGTi]

Ok,I have a fault with my B5,EPC light comes on,limp mode wont rev above 1500,but here is the rub,it's not all the time. My mechanic put the car on the diag computer and it came up it needed throttle body reset,no other fault codes,this was done and fault cleared,test drive went well all seemed good but fault is back EPC light on and limp mode,looking about this seems to point to crank speed sensor,is this likely as no fault codes for this sensor are coming up? Thanks in advance.