Sounds like it could be the HIP Module
Quote:
How it works
To calculate the vehicle's position (Host Independent Positioning), navigation data are computed on the following basis:
The HIP module receives Almanac data from the GPS aerial for
-Date
-Time
-Location of the GPS satellites
-Orbits
Operational capacity of the GPS satellites
Almanac data are selected in the HIP module and transmitted to the navigation system. With the yaw-rate sensor in the CCC, the values for change of direction (yaw rate) of the vehicle are determined. The following values are calculated from the data:
-Longitude
-Latitude
-Altitude above mean sea level
-Direction
Speed
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Link to newTIS info
Link to newTIS repair doc
EDIT** They aren't super cheap if that's what it ends up being.
ECStuning has them for $320, but maybe eBay or salvaged would be cheaper.