Cadillac 2011 STS Owner's Manual page 464

This legal identifier is in the front corner of the
instrument panel, on the driver side. It can be seen
through the windshield from outside. The VIN also
appears on the Vehicle Certification and Service Parts
labels and certificates of title and registration.
The eighth character in the VIN is the engine code. This
code identifies the vehicle's engine, specifications, and
replacement parts. See Engine Specifications under
vehicle's engine code.
6-114
This label, on the spare tire cover, has the following
information:
Vehicle Identification Number (VIN)
Model designation
Paint information
Production options and special equipment
Do not remove this label from the vehicle.
for the
Add-on equipment can drain the vehicle battery, even if
the vehicle is not operating.