Mitsubishi Electric error codes, explained
Mr. Slim / M-Series mini-split systems. Codes below: E/P/U codes and blink patterns (E6…). Each guide covers what the code means, what you can safely try yourself, when to stop and call a technician, and what the repair typically costs.
Mitsubishi E6 — Indoor/outdoor unit communication error
The indoor head and outdoor unit stopped communicating. Causes range from a power blip to wiring faults between units, or a failing control board. On Mr. Slim systems this is one of the most common fault codes.
Mitsubishi P-codes and blinking lights — Indoor-unit fault family
P-series codes (and equivalent indoor-unit LED blink patterns) are indoor-unit-detected faults: P1/P2 are thermistor (sensor) faults, P3 is a communication error, P4 is the float switch open, P5 the drain pump, and P6 freeze/overheat protection. The office classic is P4/P5 — the condensate drain system shutting the unit down before it leaks through the ceiling.