Mitsubishi Electric ductless-mini-split — Mitsubishi Electric indoor units that publish the P-series fault table, covering Mr Slim and M-Series indoor equipment Error Codes Directory

Mitsubishi P1: the room sensor the whole control loop depends on

P1 reports that the indoor intake air thermistor is reading outside the range the control accepts, which the reference describes as an open circuit, a short circuit, or a detached connector. The reading matters because the intake air sensor is what the system calls room temperature, so once it is untrusted the control has no basis for deciding capacity and stops rather than guessing. Applies to: Mitsubishi Electric indoor units that publish the P-series fault table, covering Mr Slim and M-Series indoor equipment This reading covers Mitsubishi Electric indoor families that publish the P-series fault table. Mitsubishi Heavy Industries equipment is a separate manufacturer with its own table, and a P1 shown by a third-party controller wired to a Mitsubishi indoor unit is not the same entry. Confirm the indoor model code before acting on it. Owner-safe checks: Compare the room temperature the controller displays with a separate thermometer placed near the indoor unit intake, and write both values down. | Confirm the front panel and filters are fully seated and closed, since a partly open panel changes what the intake sensor is exposed to. | Record the blink pattern or controller display, the indoor address, and whether the fault follows any recent maintenance. Qualified technician: Measuring thermistor resistance, inspecting board connectors, and replacing a sensor harness require the indoor electrical enclosure to be opened by a qualified technician. | If P1 is accompanied by a burning smell, visible discoloration, or a tripping circuit protective device, isolate the unit and stop using it until it has been inspected.