A method for operating a powertrain system including a torque machine mechanically coupled to an internal combustion engine includes, upon detecting a pending fault associated with a power switch configured to control power flow to the torque machine, disabling torque output from the torque machine and executing retry events. The retry events are iteratively executed with a debounce time period preceding each retry event. Presence of a fault associated with the power switch is detected when a quantity of the retry events during a time window exceeds a threshold.