Methods, program products, hybrid, and non-hybrid vehicles are provided for providing diagnostics for a direct current (DC) converter of the hybrid, and non-hybrid vehicle. The vehicle includes an engine, a rechargeable energy storage system (RESS), the direct current (DC) converter, and a controller. The engine is automatically turned on and off based on driver inputs in accordance with an auto-stop feature. The RESS at least facilitates turning on the engine. The DC converter is coupled to the RESS. The controller is coupled to the DC converter, and is configured to determine a status of the engine, receive a DC converter voltage value from the DC converter, and provide diagnostics for the DC converter based on the engine status, RESS voltage, and the DC converter voltage.