The contact owns a 2006 Cadillac CTS. The contact stated that while driving with the cruise control set to 75 MPH, the vehicle was shuddering, and the engine was misfiring. The vehicle was taken to an independent mechanic who determined that the computer was not communicating with the vehicle. The vehicle was taken to the local dealer where it was diagnosed and determined that the computer had malfunctioned. The vehicle was not repaired. The manufacturer was called but the phone disconnected. The failure mileage was approximately 181,475.