"check engine" light flashes

Hello all, my baby, a 94 GTI check engine light flashes steadily but it does not remain on. The guy I've recently bought it off, said that it first appeared when the stereo was fitted, the engine does not overheat or has performance issues I believe it could be an earthing problem on some wire could have mistakenly been cut, Ive removed the F/I fuse in the engine comparment and it extinguishes the light. Any ideas are greatly appreciated.