: Speedomoter Reads wrong

06-09-09, 01:01 PM
What would cause a speedometer to read higher that the speed I am actualy going in a 2002 cadillac deville? I also have the dash set on mph and not kmh.

06-09-09, 01:08 PM
Did you change your tire size?

06-09-09, 01:21 PM
No, it has the factory tires on it. When I hooked up the scanner the scanner woub be accurate but the car would read 40 to 50 mph higher.

06-09-09, 02:01 PM
The odds are pretty high that, your post not withstanding, your dash is set on metric rather than English units.

06-09-09, 02:19 PM
................and you don't need a scanner. It's all built into your car. Read the sticky thread at the top of the Forum entitled "How to pull codes", link and scroll down to the link for "...........OBD-II".