I had a similar issue about a week ago. We have had a LOT of snow and icey weather in Colorado the last week and that combined with haveing some fun out in the open fields offroad left the undercarriage of the vx completly gunked up and icy. My TOD was going to rear only then flashing randomly to 50/50 the evidently giving up and staying in rwd with the TOD "check" light on.

I just took it to car wash and pressure cleaned underneath. I have not had a problem since.

I think the bowling ball sized clumps of ice gunk plus the sub zero temps the last few days are pushing the hardware to its limits.

I hope this helps.

As far as cleaning the sensors you would have to take them apart and from what I have read its usually the kind of thing that ends up destroying the sensors. You could by a replacement set off a trooper on eaby for a decent price but