ecu code 4

i have a b16 in my crx... I cannot rev passed 3.... it is like my rev limiter is set at that point...i used a friends ecu and the same thing happened.. my pr3 ecu is blinking 4 times... i think it is the code for the crank angle sensor.... does anyone know what i can do to fix this problem...i also installed a msd system can that be the problem?? how hard is it to replace the crank angle sensor??

i have a b16 in my crx... I cannot rev passed 3.... it is like my rev limiter is set at that point...i used a friends ecu and the same thing happened.. my pr3 ecu is blinking 4 times... i think it is the code for the crank angle sensor.... does anyone know what i can do to fix this problem...i also installed a msd system can that be the problem?? how hard is it to replace the crank angle sensor??
if you just put the msd in and it wasnt doing this b4 check your wirring. i dont know which msd you have but most likely you had to tap into your coil make sure all the wirres are ok good luck!