GMC Troubleshooting Questions? Ask a Mechanic for Answers
Both left and right trailer lights not working but both turn signals work. The trailer bulbs of course are single filament. Cruise control not working either. I'm told that this usually occurs together. Truck brake lights were working at the time of my original question but now they do not work either. I haven't checked the light bulbs on the truck yet but I will do that now.
Yes, except that the left and right brake lights do not work and the center light works.
I have studied these diagrams as well as the ones in my repair book and don't know how to proceed. Too many "black boxes" and I don't know what is going on inside them..