A telematics controller is programmed identify a location of the vehicle responsive to failure of a vehicle-originated data call to initiate packet-switched communications, and send, to a service delivery network configured to provide data services to the vehicle, a message specifying that circuit-switched communication but not packet-switched communication is available to the vehicle. A message is received, over a wide-area network from a vehicle, in response to a failed initiation of a packed-switched data connection over the wide-area network, indicating that packet-switched communications are unavailable at a current location of the vehicle. Failure zones are updated to indicate that the current location of the vehicle is a network location supporting circuit-switched communication but not packet-switched communication over the wide-area network.