1993 Buick Century NEED ADVICE ON HOW TO FIX Problem or wha

I have a 1993 buick century 6 cylinder. I have recently did an engine check and the number code 43 pop up. I know what the code says but I dont know what it means. The code says electronic spark timing (EST) circuit-low voltage detected or electronic spark control (ESC) - circuit problems. Can you please tell me what this means. Thank you.