A method of operating an Uninterruptible Power Supply (UPS) system can be provided by activating an idle state for a UPS module included in the UPS system and providing a UPS module test input to the UPS module in the idle state. A UPS module test response can be provided from the UPS module in the idle state, to the UPS module test input. The UPS module test response can be compared to a predetermined UPS module test response and the UPS module can be identified as a potentially faulty UPS module responsive to determining that the UPS module test response varies from the predetermined UPS module test response by more than a threshold value.