My friend has this same problem with his Tahoe. Not sure if its the same problem, but there is a recall on some GM trucks that have a problem like you describe. The fix is to change the speedompter cluster.

 

if its still under warranty take it back to the dealer.

 

same issue

Having same issue on same Model but it doesn't always do it and dealer said they couldn't find anything wrong... So going to take picture of it reading 30 mph while in park, But does anyone know what issue could be ??? computer ???

 

Having same issue on same Model but it doesn't always do it and dealer said they couldn't find anything wrong... So going to take picture of it reading 30 mph while in park, But does anyone know what issue could be ??? computer ???

had same problem, have the unit rebuilt I did at local dealer , it was about 200 $ us, beats 1500$ us for replacement