E01 on a Toshiba heat pump: No communication between hydro unit and remote controller (detected by remote controller)
Short answer
On a Toshiba heat pump, E01 means: No communication between hydro unit and remote controller (detected by remote controller). The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 3 sources
What it means
On the R32 Estia 1-Series (split, Wall-Mounted and All-in-One)
The manual says: No communication between hydro unit and remote controller (detected by remote controller).
Part involved: remote controller and its cabling.
When it shows: Remote controller cannot receive from hydro unit.
Likely causes:
- Remote controller crossover wiring.
- Remote controller.
- Hydro power supply wiring.
- Water heat exchanger board.
On the Estia 5 Series (Standard)
The manual says: No communication between hydro unit and remote controller (detected by remote controller).
Part involved: remote controller and its cabling.
When it shows: Remote controller receive fault.
Likely causes:
- Remote controller crossover.
- Remote controller.
- Hydro power supply wiring.
- Water heat exchanger board.
On the Estia 5 Series Powerful (Hi Power / Extreme)
The manual says: No communication between hydro unit and remote controller (detected by remote controller).
Part involved: remote controller and its cabling.
When it shows: Remote controller receive fault.
Likely causes:
- Remote controller crossover.
- Remote controller.
- Hydro power supply wiring.
- Water heat exchanger board.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: yes (per manual).
Manual reset: Clear the code from the remote controller once the cause is fixed (service procedure).
What you can check
- Note the check code shown on the remote controller and the outdoor/hydro model numbers before contacting an engineer.
- Check the consumer-unit breakers/isolators for the outdoor unit, hydro unit and backup heater are switched on.
What the engineer will check
On the R32 Estia 1-Series (split, Wall-Mounted and All-in-One)
- Follow manufacturer's check-code flowchart.
- Remote controller crossover wiring.
- Remote controller.
- Hydro power supply wiring.
- Water heat exchanger board.
Who to ask for: Heat pump engineer.
Certification: None specific.
On the Estia 5 Series (Standard)
- Follow manufacturer's check-code flowchart.
- Remote controller crossover.
- Remote controller.
- Hydro power supply wiring.
- Water heat exchanger board.
Who to ask for: Heat pump engineer.
Certification: None specific.
On the Estia 5 Series Powerful (Hi Power / Extreme)
- Follow manufacturer's check-code flowchart.
- Remote controller crossover.
- Remote controller.
- Hydro power supply wiring.
- Water heat exchanger board.
Who to ask for: Heat pump engineer.
Certification: None specific.
What you might notice
Sources
- Air to Water Heat Pump Service Manual - Wall Mounted Type (File No. AE0-2101W) ↗ · AE0-2101W · page p.119 (printed page; PDF page +1) · Reviewed 23 September 2026
- Air to Water Heat Pump Service Manual (File No. A10-1704) - Estia 5 Series Indoor/Outdoor ↗ · A10-1704 · page p.93 (printed page; PDF page +1) · Reviewed 23 September 2026
- Hydro Unit Installation Manual EF99812301-4 (Powerful) ↗ · EF99812301-4 · page p.62 (printed page; PDF page +1) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026