What PB means
The indoor unit's fan motor has an error.
Also shown as: Pb, 11 blinks, depending on the model.
Likely causes
- Fan motor fault
- Obstruction
Safe first checks
- Turn the system off and check for anything visibly stuck in the indoor unit's air outlet, without reaching inside.
When to stop
Fan motor repair is for an HVAC technician.
Checked against: Mitsubishi Electric, Mr. Slim indoor/outdoor unit malfunction-diagnosis check codes (2024-11-18). Codes can differ by model and year, so confirm with your owner's manual.