E1 on a Mitsubishi Electric heat pump: Main remote controller control board failure - cannot access non-volatile memory
Short answer
On a Mitsubishi Electric heat pump, E1 means: Main remote controller control board failure - cannot access non-volatile memory. The heat pump stops until the fault clears or is reset. 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: Main remote controller control board failure - cannot access non-volatile memory.
Part involved: Main remote controller board.
When it shows: Main remote controller control board failure - cannot access non-volatile memory.
Likely causes:
- Fault with main remote controller circuit board.
On the Ecodan Co2 Quhz
The manual says: Main remote controller control board failure (non-volatile memory).
Part involved: Main remote controller / cable.
When it shows: Main remote controller control board failure (non-volatile memory).
Likely causes:
- Transmission cable contact failure; wiring procedure not observed (500 m max, 2-core); FTC or remote controller board fault; electrical noise; (E1/E2: remote controller board fault).
Is it safe?
On the Ecodan
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
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? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
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
On the Ecodan
- 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.
On the Ecodan Co2 Quhz
- 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
- Replace main remote controller (circuit board).
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan Co2 Quhz
- Check cable/connections; power indoor and outdoor off/on; replace FTC and/or main remote controller board (E1/E2: replace remote controller board).
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
What you might notice
What owners and engineers report
28 owner and engineer reports mention this.
- Controller / thermostat problem on the Ecodan: 14 reports
- No heating on the Ecodan: 9 reports
- Controller display blank on the Ecodan: 5 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 40 (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