Gen 4 Prius Navigation System changes by itself to metric units

[MRVHBig]

I have a new 2017 Prius Generation 4, Excel trim, purchased in July. There is a strange, minor but irritating fault with the GPS navigation system. At random intervals, but at least once per week it switches to metric measurement units, displaying speed limits in kilometres rather than miles. The main driving display (speedometer, etc.) is unaffected, and continues to show mph. I can easily set it back to using miles and yards, but it is irritating and mysterious. I have downloaded and applied the updated software version 6.9, and that hasn't cured what seems to be a software bug.
Has anyone heard of this issue before?

[PeteB]

I've had it happen about twice in 15 months and 19,000 miles.

At that frequency its just mildly irritating at the time (especially as I only use the internal SatNav as backup, and primarily rely on my TomTom).

I've never updated the software in the car, and won't until I hear a number of people say:

1. there's some useful improvement
2. nothing is made worse by the update (e.g. USB stick music problems)

[ian rooke]

Hi I have had this happen about 5 time in 18 months I have installed all updates as they come and had no  improvement I just hope they fix it before the free updates run out but I won't hold my breath 

[PeteB]

Maybe I've seen it so little because I look at the internal SavNav so rarely.

I tend to set it up on longer journeys so that if my TomTom suction mount comes off the beanbag, I can use the built in SatNav until I can pull over and remount the portable one.

[ian rooke]

Hi same here use Sat Nav less than once a month so if used more it should change more

[MRVHBig]

Thanks for the comments. It isn't only my car that's affected.