Heat pumps · Error codes · Hitachi
YCC-03Hitachi · Hitachi, all models
YCC-03 on a Hitachi heat pump: Lost communication with all slave YUTAKI units (YUTAKI Cascade Controller)
Short answer
On a Hitachi heat pump, YCC-03 means: Lost communication with all slave YUTAKI units (YUTAKI Cascade Controller). The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Lost communication with all slave YUTAKI units (YUTAKI Cascade Controller).
Part involved: YUTAKI Cascade Controller.
Likely causes:
- Loose, disconnected, broken or short-circuited connector.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: unknown.
What you can check
- Read and note the alarm code and any retry code (e.g. P70) shown on the unit controller.
- Check the heat pump supply breaker/isolator at the consumer unit is ON.
- Restart once via the unit controller (or switch off/on at the isolator) - the manual states the unit must be stopped to release most alarms; if the code returns, call an engineer.
What the engineer will check
- Follow SMGB0146 section 6.7 troubleshooting flowchart for alarm 03.
- Check H-Link / transmission wiring polarity, continuity and terminal tightness.
- Check PCB fuses and DIP-switch/address settings.
- Check power to the other unit (outdoor/indoor/controller).
Who to ask for: Heat pump installer / service engineer (controls wiring).
What you might notice
Sources
- Installation & Operation Manual - YUTAKI series and YUTAKI Cascade Controller (R410A series / R32 series) ↗ · PMML0510 rev.1 - 10/2019 · page p.148 (PDF p.159) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026