When I reach 80 MPH, a message comes up and says there is an 80 MPH limit? on 2006 Buick Lucerne

I had it at a dealer and they found nothing wrong, they say.

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2 answers
the speed limit is 70mph
I believe you can go into the settings on the dash and change the speed limit setting. Look at the owners manual. I do not remember how. I do remember one thing very well. When you have lazy mechanics and service advisors you will get silly ass answers like the one they gave you.