2006 Saturn Vue needed new alternator and battery. After they were installed my odometer reading decreased by about 30,000 miles. Could it have switched to km instead of miles? How do I reset?

SOURCE: 08 Chevy Cobalt - Change Odometer from KM back to MI

Put key in on position with engine off.
Hold Info & Back button together for a few seconds on steering wheel.
Scroll thorugh with info button Till you see it say Kilometers.
Hold Back Button.
Should Change

SOURCE: Change odometer display from miles to km's

there should be a menu button some where on the dash that will let you select it also it might have the gauge with both mph and km on it your owners manul should tell you how to change it

SOURCE: Replaced battery on 98 Porsche Boxster and now odometer is wrong

I had the same problem and was about to take the car to the dealership tomorrow, but I decided to try disconnecting the battery and see if it would reset itself. When I reconnected the battery the odometer mileage went back to where it was before I changed the battery. It worked!

Maybe it will work for you. Good luck!

SOURCE: 2003 Saturn L300 odometer reads 694,278 miles and

change the whole instrument cluster with one from a wreck.

SOURCE: 2005 Saturn Vue, no light in odometer, is odometer

Hi:
the dash has seven or eight small bulbs illuminating the entire area, and approx 3 of them are for the speedometer/odometer area.

It seems odd that those are the first to go, but most likely the problem.
It often requires removal of the instrument cluster to swap bulbs. not too bad, but sometimes tricky.