99 Chevy Express cruise control problem

I have a problem with my cruise control. It works about 70 percent of the time with the lights off. If turn the lights on it cancels the cruise control. It did work before with or without headlights. Just noticed also daytime running lights arent working. Wonder if there related?

I have a problem with my cruise control. It works about 70 percent of the time with the lights off. If turn the lights on it cancels the cruise control. It did work before with or without headlights. Just noticed also daytime running lights arent working. Wonder if there related?

May bee.
Needs to be put on a full capable professional scanner to check out for problem.

Tailights (parking light circuit) could be backfeeding into brake light circuit- (which always cancels cruise control when brake is depressed) - look for trailer wiring to be crossed up, or even the wrong bulb, or right bulb installed wrong in tailight assembly.

Has anyone been "working on" tailights or trailer wiring?

Heck, I've seen this after a fuel pump replacement- where the tailight wiring conduit got pinched between gas tank bracket and the frame rail- green and brown wires were smashed so hard they connected inside conduit- and both circuits were energized when either was requested....

Thaks for the reply. No trailer hitch and while the fuel pump was just replaced it has been going on for a yaer or two. I will look at the tailights to see if there working correct. Is there a running light relay with this van? I know there is on the Blazer.