Logically speaking, you're of course quite right. But given the inconsistency across the speed range, it's still hard to ignore, 'just in case it might be right this time'. It's hard to look down at the speedometer and see it reading 135 kmh and still tell yourself not to worry because 'you're really doing 120' (which even of itself is on the edge of 'detect and ticket').

Hope the dealer has the mechanism to assess and recalibrate.

 

So do I, I certainly would like the most accurate device especially concerning mileage. Good luck

 

If you are off by that much, I'd also be concerned with accumulating extra mileage on the odometer. Your warranty and maintenance and everything will expire sooner and be off.

 

Without getting into your the particulars of your "guesstimate" comment, unless you have a time machine handy, there is no GPS induced distinction made between military and civilian receivers.

And there hasn't been for seven years.

 

Any diagnostic like this on non-nav cars?

 

Cool! Although not too much there that sounds useful. The error history stuff might be useful if you have problems.

Are these diagnostics initiated the same way as in the Nav car?

Is all of this stuff in the service manual that was posted earlier on this site, or are you getting this from somewhere else?