How to Fix HMS 0500-0300-0001-0002: MC Module Firmware Version Mismatch

Bambu Lab HMS error code 0500-0300-0001-0002 is an MC module firmware version error within the 0500-0300 system subgroup. Unlike the base communication failure in 0001-0001, suffix 0001-0002 indicates communication with the MC module was partially established but the versions of the AP firmware and MC firmware are incompatible.

What the Error Means

The application processor (AP) and motion controller (MC) firmware must match to a compatible version pairing. When they do not, the AP can detect the MC module but the two cannot coordinate because their protocol or data structures differ. This most often occurs after a firmware update that only partially completed — for example if a power loss interrupted the update mid-process, or if a manual flash was applied to only one board. It can also occur if someone installs a beta firmware that has a different MC pairing.

Step-by-Step Fix

  1. Power cycle the printer. On the next boot, the printer may detect the mismatch and attempt to push the correct MC firmware automatically.
  2. Navigate to the firmware update screen. If an update is shown, install it — this will re-flash both the AP and MC firmware together, correcting the version mismatch.
  3. Ensure the printer has a stable internet connection before attempting the update. Use a wired Ethernet connection if Wi-Fi is unreliable.
  4. Do not power off the printer during the firmware update process. A second interrupted update will worsen the situation.
  5. If the printer cannot start an OTA update, check the Bambu Lab community wiki for a USB recovery procedure for your model to restore firmware from a known-good image.
  6. After the update completes, confirm the firmware version shown in the settings matches the expected release version.
  7. Run a short test print to confirm normal operation.

Parts Required

No replacement parts are typically required for this fix — basic tools only.

If firmware re-flashing does not resolve the version mismatch, a hardware fault may be preventing the MC module from being updated — contact Bambu Lab support.