Chevrolet Repair: 84 blazer CODE 42 cant fix, crank sensor, reluctor

Question
Hey guys I have a 84 blazer, the first year with the ECM and EST. I keep pulling code 42 after my truck with spontaneously die in the middle of the road while driving. It does it very spontaneously, manual says "electronic spark timing bypass circuit is grounded or open" where should I look to fix this?

Answer
Hi Mitch... trace the circut and see if you can find the open or ground...i would look at crank sensor first and work up...check reluctor is not touching sensor or dirt in it. also check est module at the dist. they are known to go...hope this helps...merry christmas