ONSTAR Vehicle Communication Unit (VCU) Replacement: Notes

NOTE: Never swap OnStar® Vehicle Integration Units (VIU), or the Vehicle Communication Units (VCU) from other vehicles. Transfer of OnStar® components from other vehicles should NOT be done. Each OnStar® component has a unique identification number. The VIU has a 10-digit Specific Station Identification (STID) and the VCU has a 11-digit specific Electronic Serial Number (ESN). These identification numbers are used by the National Cellular Telephone Network and OnStar® systems, and are stored in the General Motors vehicle history files by VIN.