GM Full-Size Trucks 1988-1998 Wiring Diagrams Repair Guide Your Destination for GM Truck Parts. We hope you found the 1995 Chevy G20 wiring diagrams and other schematics helpful. When you’re ready to start your project, count on AutoZone’s large selection of auto parts and accessories by Autolite, Bosch, NGK, Duralast, Blue Streak, ACDelco, and other respected industry manufacturers. 2003 & 2004 MEDIUM DUTY C SERIES ELECTRICAL PDF file• Subsystem Schematics – Detailed wiring and electrical schematic information. WHAT’S NEW FOR THE MEDIUM DUTY C SERIES •A Component Locator page has been included to show the location of major electronic modules on the truck. C7500 with brake lite and ABS light on - Tow411 I cant find a wiring diagram to trace the whole system. Any help would be helpful!!!!! tatersalad72. 289 - - tatersalad72. 289. Post Apr 13, 2010 #2 2010-04-13T19:27. I had an 05 C6500 with the same problem? Mine came on after an aftermarket radio was installed? Seems the radio communicates with other components???? Good luck, David B & D Wrecker.