Oh okay my database must be wrong then. It doesn't show anything about stability control for a 2006 Montana.
Okay, this is called Stabiltrak and it's not separate from traction control and ABS, but it's more than just those systems. Here's a brief description of Stabiltrak:
" Three key sensors keep the ABS and traction control computer informed: one reads steering wheel angle, another reports the vehicle’s lateral acceleration and the third measures yaw rate (rotational velocity about a vertical axis through the car’s center of gravity). Information is also gathered from vehicle speed.
But to the problem at hand. What error codes were scanned? Do you have those error codes perchance? That would be helpful. Apparently, one or more of these sensors is sending false data, wouldn't you think?