On my 2009 Yukon, I always felt the cruise control was fluctuating around my set speed +/- a few MPH, on flat interstate roads. I would notice cars around me speeding up/slowing down, thinking it was them. My speedo would never fluctuate any more than +/- 1 MPH.
While traveling with a friend in his Honda CRV, he noticed that I would speed up/slow down +/- 2 to 4 MPH while on cruise (driving him nuts).

Anyone else experience this? I'm wondering if the speedo/computer is "lying" to the driver while on cruise, and cannot maintain accurate control?

 

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Are you driving in a hilly area? Hilly areas can affect how the cruise control functions, whether the roads are flat or not.

How well the cruise control will work on hills depends upon the vehicle speed, load, and the steepness of the hills. When going up steep hills, you might have to step on the accelerator pedal to maintain the vehicle’s speed. When going downhill, you might have to brake or shift to a lower gear to keep the vehicle’s speed down. When the brakes are applied the cruise control turns off.

If this issue persists, I recommend having the vehicle inspected by a certified technician.

Please feel free to contact me if you have additional questions.

Louis
GM Customer Service

 

I think he said he notices the problem on flat interstates.