The control system software plays an increasingly important role in achieving overall accelerator system reliability, in this regard the CLS control system is no different. This paper reviews the two aspects of control system reliability (1) the reliability of the control system itself and it contribution to system reliability and (2) the use of the control system as a tool to aid in predicting and localizing system failure therefore providing an indirect impact on mean-time-between-failure and mean-time-to-repair. The paper provides a survey of metrics used at the CLS to evaluate system reliability, several failure modes that have been localized and removed from the system design to contribute to overall reliability. Recently CLS has deployed a new approach to alarm annunciation and fault location based on voice annunciation and nested dashboard display screens.