4x4 light on, again
 

A week ago the 4x4 yellow light on the dash came on, as someone suggested I did the wheel lock to lock, and it went off...well it's on again.
Could the fact that I only replaced the rear tires (same size different brand) have anything to do with that? The fronts have over half tread still left.
What happens if we just keep driving it with the light on?

That's been my experience with tire wear and I did not experience any problems. I will go through two sets of rears for every one set of front tires. I have the staggered setup but I don't think that matters in this comparison. So, like you, I replace the rears when the fronts are only half worn.

Are you able to reset the 4x4 light now like last time? Me I would check that you didn't damage any sensors when you replaced the rear tires. I would also try and get it scanned with GT1 or equivalent to see what codes come up. The GT1 is nice because it helps with diagnosis a lot by giving you a step-by-step test plan.

It usually takes an overall tire/wheel diameter or circumference difference of 3% (+/-) to cause issues with the ABS/DSC/speedometer/odometer systems. This can be on a side-to-side axle situation or a front-to-back axle situation.

If the situation is like in the first image below from the owners manual...then take note of the text that is NOT highlighted as for what could be wrong. Without having any diagnostics done to pin point which control modules have set a fault...it could be your ABS/DSC/braking system, the x-drive system, or the hill descent functions.


If it comes on and stays continuously lit:
If the light flashes or stays on continuously after pressing the button (intentionally or unintentionally):



If it come on with other warning lights:

I guess I'll have it over to my "indie" and have him put the computer on it....

The shop cleared the codes, now to see what happens....car is 7 weeks out of CPO warranty SEVEN WEEKS "how do it know...." (06 3.0 55,000 miles)
Anyway he says that is common fault...steering angle sensor approx a $500 fix (keeps the part is stock!)
This really pisses me off, tell me that BMW NA doesn't know about this.
If the code comes back I think I'll take it over to the local dealer and see what they say....