C09 means the lid lock is not releasing on the Hitachi washer referenced. Wait for safe conditions and follow the model’s unlocking procedure without pulling on the lid.
The Hitachi FAQ distinguishes C09 from open-lid messages. Here the problem is regaining access, not getting it to close and start.
Before trying to open it
Check whether the cycle has stopped and whether spin, water, or temperature may still be keeping the safety lock engaged. Do not insert tools into the latch or assume that cutting power will cause it to open immediately.
Use only the pause or recovery method specified in the reference manual. Emergency releases and their access points are not universal across all Hitachi models and should not be copied from another brand.
If the lock still will not release after the permitted procedure, request service. Keep C09 noted and record whether it happened after a power outage, during the cycle, or at the end; that context helps distinguish normal operating sequence from a persistent fault.
Keep the laundry inside until there is a safe way to open it; forcing the lid can add damage and release water uncontrollably.