Mitsubishi Ecodan fault codes

59 codes from the Mitsubishi manual for the Ecodan heat pump. Pick one for what it means, the likely causes and where to start.

Code	What it means
1	Main remote controller display is blank
10	Temperature of DHW tank water dropped
12	Water leakage
13	Heating system does not reach the set temperature
14	In 2-zone temperature control, only Zone2 does not reach the set temperature
15	When a PUHZ-FRP outdoor unit is connected, DHW or heating operation cannot run
16	When a PUHZ-FRP outdoor unit is connected and in heat recovery operation, the set...
19	Water discharges from pressure relief valve (primary circuit)
2	'please wait' remains displayed on main remote controller
20	Water discharges from pressure relief valve (sanitary circuit)
23	Noisy water circulation pump
25	Mechanical noise heard coming from the cylinder unit
26	Water circulation pump runs for a short time unexpectedly
3	Main screen appears then disappears after pressing ON button
33	L6 error (circulation water freeze protection error) occurs during DHW or LP mode...
34	The energy monitor value seems not correct
4	LED2 on FTC is off (FTC powered on independent source)
5	LED2 on FTC is blinking
6	LED4 on FTC is off
7	No water at hot tap
8	Cold water at tap
9	Water heating takes longer
E0	Main remote controller communication failure (reception error)
E1	Main remote controller control board failure
E2	Main remote controller control board failure
E4	Main remote controller communication failure (reception error)
E5	Main remote controller communication failure (transmission error)
E8	Applicable error for automatic backup heat source operation
E9	Applicable error for automatic backup heat source operation
ED	Applicable error for automatic backup heat source operation
J1TOJ8	Wireless remote controller/wireless receiver communication failure (reception error)
L3	Circulation water temperature overheat protection
L4	Tank water temperature overheat protection
L5	Flow/return/tank/zone water temperature thermistor failure
L6	Circulation water freeze protection
L8	Heating operation error (code 3 - main circulation)
L9	Low primary circuit (Zone2 side) flow rate detected by flow switch
LC	Boiler circulation water temperature overheat protection
LD	Boiler temperature thermistor (THWB1, THWB2) failure
LE	Boiler operation error
LJ	DHW operation error (type of external plate HEX)
LL	Setting errors of DIP switches on FTC control board
P1	Indoor unit temperature thermistor (TH1) failure
P2	Indoor unit temperature thermistor (TH2) failure
P6	Anti-freeze protection of plate heat exchanger
P8	Applicable error for automatic backup heat source operation
U1	Applicable error for automatic backup heat source operation
U2	Applicable error for automatic backup heat source operation
U3	Applicable error for automatic backup heat source operation
U4	Applicable error for automatic backup heat source operation
U5	Applicable error for automatic backup heat source operation
U6	Applicable error for automatic backup heat source operation
U7	Applicable error for automatic backup heat source operation
U8	Applicable error for automatic backup heat source operation
UD	Applicable error for automatic backup heat source operation
UE	Applicable error for automatic backup heat source operation
UF	Applicable error for automatic backup heat source operation
UL	Applicable error for automatic backup heat source operation
UP	Applicable error for automatic backup heat source operation