95civic_ferio

ok first off i have a 1995 d15b7 motor. did a mini me using a d15b7 block with a y8 head and a z6 manifold also with a ex/si tranny. the car runs great and vtec hits i'm assumming because i know single cam vtec doesnt hit as hard but i have a CODE 4 which is CKP - crank position sensor. I'm also using a stock p28 ecu. I honestly do not know how to get rid of this code. to my knowledge the d15b7 doesnt have that sensor behind the crank pulley? should i just ignore it or should i do something about it. car still runs and drive great. any opinions would be greatly appreciated!