s13 twincam ....no tach signal...code 21

[DRIFTA X]

ok Im really hopin some one can help menow i have an s13 and im getting code 21......now im an intaller....autostarts sound systems etc...u name it i can install it on or in a car...ok now im gettin code 21....now every thing is new...plugs wires etc....i changed the distributor that to my knowledge was good....i removed the msd and put back the factory coil......still nothingif i attempt to simulate a tach signal ie tapping ground on negative side of coil car wants to start.......the only code is 21.....so im trying to get another distributor......i also did the proceedure from the fsm lookin for continuity and it was good...so if any one can help ill appreciate it