CORRODED, BROKEN, OR SHORTED WIRES WILL ALWAYS CAUSE ISSUES.
The corrosion will not allow the electrons to flow properly, increasing the resistance on the circuit, and decreasing voltage and amperage.
Broken wires, well, obviously wont allow any voltage to pass, and can lead to shorts....all of this can cause all sorts of havoc in an electrical system.
Patch, fix, or otherwise replace the broken/ corroded sections of wire in the harness, and you should be good to go.

Good luck!