A mobile device may implement an idle mode process in order to selectively scan for legacy radio coverage using a timer-based scanning process. A mobile device may operate in idle mode and may establish a long term evolution (LTE) radio link with a nearby cell site. The idle mode process implemented by the mobile device may include evaluating one or more criteria that are indicative of whether the mobile device is capable of providing sufficient voice service capabilities using voice over LTE (VoLTE). Based on the criteria evaluation, a timer-based scanning process may be initiated. When the timer-based scanning process is initiated, the mobile device may scan for legacy radio coverage periodically. If no legacy radio coverage is available, the mobile device may indicate that voice services are unavailable.