J0 on a Mitsubishi Electric heat pump: Communication failure between FTC and wireless receiver
Short answer
On a Mitsubishi Electric heat pump, J0 means: Communication failure between FTC and wireless receiver. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 2 sources
What it means
On the Ecodan
The manual says: Communication failure between FTC and wireless receiver.
Part involved: Wireless receiver (PAR-WR51R-E) / FTC connection.
When it shows: FTC cannot receive data from the wireless receiver for 1 minute.
Likely causes:
- 1 Wireless receiver-FTC connection fault; 2 FTC receiving circuit fault; 3 Wireless receiver transmission circuit fault; 4 Electrical noise on receiver cable.
On the Ecodan Co2 Quhz
The manual says: Indoor unit/wireless receiver communication failure.
Part involved: Wireless receiver.
When it shows: FTC cannot receive data from wireless receiver for 1 minute.
Likely causes:
- Receiver-FTC connection fault; FTC or receiver board fault; noise.
Is it safe?
On the Ecodan
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Not stated as auto-resetting; code remains until reset.
Manual reset: Installation manuals: press F4 (RESET) then F3 (Yes) on the main remote controller (older controllers: hold button E for 3 s); 'To cancel error codes please switch system off'. Fix the cause first.
On the Ecodan Co2 Quhz
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Not stated as auto-recovering.
Manual reset: Press F4 (Reset) then F3 (Yes) on the main remote controller, or switch system off (installation manual).
What you can check
- Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. A power cycle is a Mitsubishi first step for communication codes: switching the heat pump off and on at its isolator (outdoor and indoor supplies) once is acceptable.
What the engineer will check
On the Ecodan
- 1 Check receiver-FTC cable and connections; 2-4 Power indoor and outdoor units off/on; if J0 persists replace FTC and/or receiver board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan Co2 Quhz
- Check receiver cable; power off/on; replace FTC/receiver board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
What you might notice
What owners and engineers report
14 owner and engineer reports mention this.
- Controller / thermostat problem on the Ecodan: 14 reports
Sources
- Ecodan EHPT20X-MEHEW Service Manual (OCH814A) ↗ · OCH814A · page 64 (10-4 Self-diagnosis and action) · Reviewed 23 September 2026
- Ecodan EHPT20Q VM2EA Service Manual (GCH15010C) ↗ · GCH15010C · page 41 (10-4 Self diagnosis and action) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026