1993 Chevy Suburban check engine ligt comes on

I purchase the actron code scanner. After using the scanner the code I received was a 43. That ment electronic spark timing(est)circuit-low voltage detected or electonic spark control (esc)-curcuit problems. Both the EST and the ESC say that they are controlled by the ECM electronic control module.
The vehicle has a slight hesitation, idles a little low and while driving has slight surges on and off in acceleration. It also seems to run a little rich. I've noticed some black soot on the rear bumper
What do you think I need to replace to fix the problems and to clear the check engine problem.
Thanks for your help
Paul J Carbone
727-458-8139 cell number