What happens if an ATLAS flash is interrupted or fails?

An interrupted flash is the failure mode worth understanding before you ever start one, and the honest answer is reassuring with one significant caveat. **What normally happens.** On Subaru WRX models from 2015 onward, the ECU bootloader runs logic at startup that checks whether the flash completed correctly by examining the first and last sections of the programmed ROM. If those sections are not right, the ECU enters recovery mode. In recovery mode the ECU cannot operate the vehicle - the car will not run - but it is waiting to accept a new upload. So an interrupted flash typically leaves you with an immobile car rather than a destroyed ECU, and the fix is to complete a successful flash. **What causes it.** Two things dominate: losing power to the ECU during programming, usually from a low battery, and disconnecting the OBD adapter while the flash is running. Both are entirely preventable. **The caveat that VB owners need to know.** On ATLAS versions 2024.4 and earlier, recovery is not possible on 2023+ WRX manual transmission ECUs. ATLAS 2025.1 and later resolves this upon first programming with the ECU. If you own a 2023 or newer manual VB, make sure you are running a current version of ATLAS before your first flash. This is not a minor version-number detail - it is the difference between a recoverable situation and a genuinely bad one. **How to avoid the situation entirely.** Connect a high-amperage battery charger before you start, or at minimum ensure the battery has ample capacity to supply the electrical system for at least 30 minutes with headlights and auxiliary components switched off. Do not touch the adapter, the laptop or the ignition during programming. Close anything on the laptop that could pop up, sleep the machine or steal focus. Sit still and let it finish. If you do end up in recovery mode: do not panic and do not start disconnecting things. The ECU is waiting for a valid upload. Sort out whatever caused the interruption - almost always battery voltage - and flash again.