Mitsubishi Heat Pump Error Codes — Meanings, Causes & Repair in Greater Vancouver

Seeing a fault code on your Mitsubishi heat pump? This guide explains what the most common Mitsubishi heat pump error codes mean, what’s safe to check yourself, and when to call HeatLand’s licensed HVAC technicians for Mitsubishi heat pump repair across Metro Vancouver and the Fraser Valley.

The codes below apply across common Mitsubishi models (MSZ, MXZ, M-Series, P-Series, Hyper-Heating H2i). Meanings follow Mitsubishi’s documented fault codes — always confirm against your unit’s own manual, because exact wording can vary by model, control board and firmware.

How to read Mitsubishi heat pump error codes

Mitsubishi Electric mini-splits self-diagnose and display two-character check codes. On systems with a wired/wireless remote, the code (E__, P__, U__, F__) shows on the remote display. On the outdoor unit, abnormalities are shown by blink patterns of LED1 (green) and LED2 (red) on the outdoor controller board, which map to the same check codes. P/E codes are generally detected by the indoor unit or remote/communication side; U codes are generally outdoor-unit/refrigerant/compressor faults; F codes are pressure-switch/connector and fan-motor faults. Codes are consistent across MSZ/MXZ residential and Mr. Slim P-Series.

Mitsubishi heat pump error codes & what they mean

These are the Mitsubishi heat pump codes our Greater Vancouver technicians see most. Anything marked pro repair involves electrical, refrigerant, sensor or control-board work that must be done by a licensed HVAC technician — never open the indoor/outdoor unit or refrigerant lines yourself.

Code	What it usually means	Common causes	Safe to check yourself
P1	Intake / room temperature thermistor (TH1) error pro repair	Failed or disconnected intake/room temperature thermistor; Loose thermistor connector on indoor control board; Indoor controller board fault	Confirm power and breaker are on; Restart at the breaker once; Confirm remote is set to the intended mode
P2	Indoor pipe (liquid) temperature thermistor (TH2) error pro repair	Failed or disconnected indoor liquid-pipe thermistor (TH2); Loose thermistor connector; Indoor controller board fault	Confirm power and breaker are on; Restart at the breaker once
P4	Drain sensor (DS) error / float switch (FS) connector open pro repair	Failed or disconnected drain sensor; Open float-switch connector; Loose wiring to indoor control board	Confirm power and breaker are on; Restart at the breaker once
P5	Drain pump error / indoor drain overflow protection pro repair	Failed or blocked condensate drain pump; Clogged condensate drain line causing overflow; Damaged drain sensor	Confirm power and breaker are on; Restart at the breaker once
P6	Freezing (cooling) / overheating (heating) protection operating — coil frost/overheat protection pro repair	Dirty or clogged indoor filter restricting airflow; Blocked indoor or outdoor airflow / short-cycling of air; Low refrigerant charge	Clean or check the indoor filter; Make sure the outdoor unit is clear of snow, leaves, or ice; Confirm indoor airflow is not blocked by furniture or curtains
P8	Abnormality of pipe temperature pro repair	Indoor/outdoor wiring connected incorrectly; Stop (service) valve closed; Indoor pipe thermistor (TH2/TH5) dislodged from its holder	Confirm power and breaker are on; Clean or check the indoor filter; Make sure the outdoor unit is clear of snow, leaves, or ice
P9	Indoor pipe temperature thermistor (TH5, condenser/evaporator) error pro repair	Failed or disconnected condenser/evaporator pipe thermistor (TH5); Loose thermistor connector; Indoor controller board fault	Confirm power and breaker are on; Restart at the breaker once
PA	Forced compressor stop (due to water-leakage abnormality) pro repair	Detected water leakage / overflow in indoor unit; Drain system fault; Drain sensor / float switch fault	Confirm power and breaker are on; Restart at the breaker once
PB	Indoor unit fan motor error (also shown as Pb) pro repair	Failed indoor fan motor; Obstructed indoor fan/blower wheel; Loose fan motor wiring	Confirm power and breaker are on; Clean or check the indoor filter; Restart at the breaker once
FB	Indoor unit control system error (memory error, etc.) (also shown as Fb) pro repair	Indoor controller board memory/control fault; Electrical noise interference; Indoor controller board failure	Restart at the breaker once
E0	Remote controller transmission error — remote controller signal receiving/transmitting error (remote does not respond to indoor controller signal) pro repair	Loose or faulty remote controller wiring (wired remotes); Electrical noise on the transmission wire; Indoor controller board or remote controller fault	For wireless remotes, replace batteries and confirm remote settings/mode; Restart at the breaker once
E1	Remote controller control board error pro repair	Faulty remote controller control board; Electrical noise interference	For wireless remotes, replace batteries; Restart at the breaker once
E2	Remote controller control board error pro repair	Faulty remote controller control board; Electrical noise interference	For wireless remotes, replace batteries; Restart at the breaker once
E3	Remote controller transmission error (signal receiving error) pro repair	Loose or faulty remote controller wiring; Electrical noise on the transmission wire; Indoor controller board or remote controller fault	For wireless remotes, replace batteries and confirm remote settings/mode; Restart at the breaker once
E4	Communication error between wired remote controller and indoor unit (remote controller signal receiving error detected by indoor unit) pro repair	Loose or incorrect remote controller wiring; Electrical noise on the remote transmission wire; Indoor controller board fault	Restart at the breaker once
E5	Communication error between wired remote controller and indoor unit (remote controller transmitting error detected by indoor unit) pro repair	Loose or incorrect remote controller wiring; Electrical noise on the remote transmission wire; Indoor controller board fault	Restart at the breaker once
E6	Indoor/outdoor unit communication error (signal receiving error) detected by the indoor unit pro repair	Indoor/outdoor connecting wire loose, miswired, or damaged; Outdoor unit powered up before indoor unit; Electrical noise on the connecting wire or power supply	Confirm power and breaker are on for both indoor and outdoor; Restart at the breaker once
E7	Indoor/outdoor unit communication error (transmitting error) detected by the indoor unit pro repair	Indoor/outdoor connecting wire loose, miswired, or damaged; Electrical noise on the connecting wire or power supply; Indoor or outdoor controller board fault	Confirm power and breaker are on for both indoor and outdoor; Restart at the breaker once
E9	Indoor/outdoor unit communication error (transmitting error) detected by the outdoor unit pro repair	Indoor/outdoor connecting wire loose, miswired, or damaged; Electrical noise on the connecting wire or power supply; Indoor or outdoor controller board fault	Confirm power and breaker are on for both indoor and outdoor; Restart at the breaker once
EE	Combination error between indoor and outdoor unit pro repair	Incompatible indoor/outdoor unit combination; Incorrect model or capacity pairing; Wrong setting after a board replacement	Restart at the breaker once
EF	Check code is not defined / undefined code (often a non-supported remote controller or noise on the line) pro repair	Incompatible or wrong type of remote controller; Electrical noise on the transmission or connecting wire	Restart at the breaker once
U1	Abnormal high pressure (high-pressure switch 63H operated) / overheat protection pro repair	Blocked or dirty outdoor coil restricting airflow; Outdoor unit short-cycling its own discharge air; Closed stop (service) valve	Make sure the outdoor unit is clear of snow, leaves, ice, and debris; Confirm at least 1-2 ft of clearance around the outdoor unit; Restart at the breaker once
U2	Abnormal high discharge temperature / 49C operated / insufficient refrigerant pro repair	Low refrigerant charge or a refrigerant leak; Closed stop (service) valve; Failed discharge thermistor (TH4)	Make sure the outdoor unit is clear of snow, leaves, and ice; Confirm airflow around the outdoor unit is unobstructed; Restart at the breaker once
U3	Open/short of discharge thermistor (TH4) and shell thermistor (TH32) pro repair	Failed or disconnected discharge/shell thermistors; Loose thermistor connectors on outdoor board; Outdoor controller board fault	Confirm power and breaker are on; Restart at the breaker once
U4	Open/short of outdoor thermistors (TH3, TH6, TH7, TH8) pro repair	Failed or disconnected outdoor thermistors; Loose thermistor connectors on outdoor board; Outdoor controller board fault	Confirm power and breaker are on; Restart at the breaker once
U5	Abnormal heat sink temperature (power module/heatsink overheat) pro repair	Blocked outdoor airflow / dirty outdoor coil; Outdoor unit short-cycling its discharge air; Failed outdoor fan	Make sure the outdoor unit is clear of snow, leaves, ice, and debris; Confirm clearance around the outdoor unit; Restart at the breaker once
U6	Compressor overcurrent interruption / abnormality of power module pro repair	Compressor wiring loose, disconnected, or cross-connected; Closed stop (service) valve; Compressor or power module fault	Confirm power and breaker are on; Make sure the outdoor unit is clear of obstructions; Restart at the breaker once
U7	Abnormality of superheat due to low discharge temperature pro repair	Linear expansion valve (LEV) fault; Refrigerant overcharge or refrigerant circuit problem; Failed discharge thermistor	Restart at the breaker once
U8	Outdoor unit fan motor protection stop / abnormal outdoor fan rotational speed pro repair	Failed outdoor fan motor; Obstructed or iced-up outdoor fan; Loose fan motor wiring (TH3 / fan connector)	Make sure the outdoor fan and unit are clear of snow, leaves, and ice; Restart at the breaker once
U9	Abnormality of voltage (e.g., overvoltage/undervoltage, abnormal main-circuit voltage) pro repair	Supply voltage too high or too low; Abnormal main circuit voltage; Power board / inverter fault	Confirm the breaker is on and the unit is on its dedicated circuit; Restart at the breaker once
Ud	Protection from overheat operation (TH3) — overheat protection pro repair	Blocked outdoor airflow / dirty coil; Failed outdoor fan; TH3 thermistor fault	Make sure the outdoor unit is clear of snow, leaves, ice, and debris; Restart at the breaker once
UF	Compressor overcurrent interruption (when compressor locked) — start-up locked pro repair	Locked/seized compressor; Compressor wiring loose or cross-connected; Closed stop (service) valve	Confirm power and breaker are on; Restart at the breaker once
UH	Abnormality of current sensor (power board) pro repair	Current sensor / power board fault; Loose power wiring; Inverter board failure	Restart at the breaker once
UP	Compressor overcurrent interruption (compressor protector / overcurrent protection operated) pro repair	Compressor wiring loose, disconnected, or cross-connected; Closed stop (service) valve; Compressor or inverter fault	Confirm power and breaker are on; Make sure the outdoor unit is clear of obstructions; Restart at the breaker once
F3	Connector (63L / low-pressure switch) open on outdoor controller board pro repair	Low-pressure switch (63L) connector disconnected; Failed low-pressure switch; Low refrigerant pressure	Restart at the breaker once
F5	Connector (63H / high-pressure switch) open on outdoor controller board pro repair	High-pressure switch (63H) connector disconnected; Failed high-pressure switch; Outdoor controller board fault	Restart at the breaker once
FC	Serial signal error between indoor and outdoor units pro repair	Indoor/outdoor connecting wire miswired or loose; Electrical noise on the connecting wire; Indoor or outdoor controller board fault	Confirm power and breaker are on for both indoor and outdoor; Restart at the breaker once

Mitsubishi heat pump codes we get called for most

P2 — Indoor pipe (liquid) temperature thermistor (TH2) error

Typical causes include failed or disconnected indoor liquid-pipe thermistor (th2); loose thermistor connector; indoor controller board fault. A few things are safe to check yourself (Confirm power and breaker are on; Restart at the breaker once), but the repair is a licensed HVAC technician job. HeatLand diagnoses and fixes P2 on Mitsubishi heat pumps throughout Greater Vancouver.

P1 — Intake / room temperature thermistor (TH1) error

Typical causes include failed or disconnected intake/room temperature thermistor; loose thermistor connector on indoor control board; indoor controller board fault. A few things are safe to check yourself (Confirm power and breaker are on; Restart at the breaker once), but the repair is a licensed HVAC technician job. HeatLand diagnoses and fixes P1 on Mitsubishi heat pumps throughout Greater Vancouver.

PA — Forced compressor stop (due to water-leakage abnormality)

Typical causes include detected water leakage / overflow in indoor unit; drain system fault; drain sensor / float switch fault. A few things are safe to check yourself (Confirm power and breaker are on; Restart at the breaker once), but the repair is a licensed HVAC technician job. HeatLand diagnoses and fixes PA on Mitsubishi heat pumps throughout Greater Vancouver.

U1 — Abnormal high pressure (high-pressure switch 63H operated) / overheat protection

Typical causes include blocked or dirty outdoor coil restricting airflow; outdoor unit short-cycling its own discharge air; closed stop (service) valve. A few things are safe to check yourself (Make sure the outdoor unit is clear of snow, leaves, ice, and debris; Confirm at least 1-2 ft of clearance around the outdoor unit), but the repair is a licensed HVAC technician job. HeatLand diagnoses and fixes U1 on Mitsubishi heat pumps throughout Greater Vancouver.

Is it safe to keep running a Mitsubishi heat pump with a fault code?

Most Mitsubishi fault codes put the heat pump into a safe lockout for a reason. You can safely check the basics — the power and breaker on, the indoor filter clean, the outdoor unit clear of snow, ice and debris, and the remote set to the correct mode and temperature — and restart it once. If the code returns, stop and book a technician. Mini-split and heat-pump faults are electrical and refrigerant issues — never open the indoor or outdoor unit, and never touch the wiring or refrigerant lines yourself.

Mitsubishi heat pump repair across Greater Vancouver

HeatLand has kept Metro Vancouver homes comfortable since 1999. Our licensed, insured technicians diagnose and repair Mitsubishi heat pumps — sensor and thermistor errors, indoor-to-outdoor communication faults, fan and compressor problems, refrigerant and pressure faults, and control-board issues — including units we didn’t install. We’re brand-agnostic, carry common parts, and give you an honest repair-or-replace assessment with upfront pricing and a free estimate. If your heat pump is beyond economical repair, we’ll show you right-sized, high-efficiency replacement options and the rebates available.

Need it sorted fast? We offer priority emergency heat pump repair. Explore Heat Pump services, browse all heat pump error codes by brand, or request a free estimate.

Mitsubishi heat pump service areas

We repair Mitsubishi heat pumps across Greater Vancouver and the Fraser Valley, including:

Mitsubishi heat pump error code FAQs

Can I reset my Mitsubishi heat pump myself?

Yes — power-cycling the unit at the breaker once is generally safe after you’ve checked the basics (the power and breaker on, the indoor filter clean, the outdoor unit clear of snow, ice and debris, and the remote set to the correct mode and temperature). If the heat pump faults again right away, stop and note the code — repeatedly resetting a heat pump that keeps locking out can mask a real problem. Call a licensed HVAC technician to diagnose it.

What does the Mitsubishi P4 code mean?

On Mitsubishi heat pumps, P4 commonly indicates drain sensor (ds) error / float switch (fs) connector open. Confirm the exact meaning against your unit’s manual — codes can vary by model and series — and have the repair done by a licensed HVAC technician. HeatLand fixes this across Greater Vancouver.

Do you repair Mitsubishi heat pumps you didn’t install?

Yes. HeatLand is brand-agnostic and services Mitsubishi heat pumps throughout Metro Vancouver and the Fraser Valley, whether or not we installed the unit. We carry common parts and give you an honest repair-or-replace assessment.

Is a Mitsubishi heat pump fault code an emergency?

No heat in cold weather or no cooling in a heat wave is worth treating urgently. For priority heat pump repair across Greater Vancouver, call (604) 330-3812.

How much does Mitsubishi heat pump repair cost in Vancouver?

It depends on the fault. Many Mitsubishi codes point to sensors, thermistors, capacitors or control parts — usually far cheaper than replacement. We give upfront pricing and a free estimate before any work.

More Heat Pump error-code guides

HeatLand repairs every major heat pump brand across Greater Vancouver. More brand guides: