A vehicle system includes a telematics control unit (TCU) coupled to a plurality of vehicle controllers. The TCU is configured to periodically record in a log wireless activity data relating to an authentication, attachment, signaling, detachment, and handover procedure of the TCU to provide one or more remote vehicle services. The TCU is further configured to, responsive to detecting a cellular malfunction from the logged data, wirelessly transmit at least a portion of the log that corresponds to the cellular malfunction offboard the vehicle for a remote server configured to diagnose operation of the TCU.