2003 venture crank sensor

I have a 2003 chevy venture. It miss fires randomally but fairly often. When it does it throws a code for crank sensor. I replaced the crank sensor and the harmonic balancer. Still hasn't fixed the problem. Also the speedomoter will also randomally work then occasionally not work. With these two problems being sparatic and seem to have no rhyme or reason it makes me believe I have an electrical issue. Any ideas?

Check your grounds out.

What was the original code that came up? A non-functioning crank sensor will kill the engine alltogether.

Thats what has me confused. Malfuctioning crank sensor is the only code that ever comes up. Check engine light will come on and stay on for a period of time then will go away the come back on and off periodically. No longer have had any speedometer issues. Just a missfire sensasion and it is also intermientant.

When do you have the missfire sensation? At Idle? At Hwy Speed? ETC?