If you have issues installing firmware on an Intel-based Mac using the SMC Firmware Updater, or, if you experienced a power loss while attempting to install an SMC firmware update, you should attempt to re-run the installer again by double-clicking it and following the instructions. The SMC Firmware Updater is located in the Utilities folder, in the Applications folder.
Reset the SMC if necessary
If re-running the SMC Firmware Updater is not successful, you may need to reset the SMC before attempting to update it again.