CJ on a Daikin Altherma HT: Malfunction of thermostat sensor in remote control
Short answer
On a Daikin heat pump, CJ means: Malfunction of thermostat sensor in remote control. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Malfunction of thermostat sensor in remote control.
Part involved: user interface / room thermostat.
When it shows: When the remote control air temperature thermistor becomes disconnected or shorted while the unit is running.
Likely causes:
- Defect of remote control thermistor; Defect of remote control PC board; Defect of indoor PC board (A1P).
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: unknown.
What you can check
- Read the full error code shown on the user interface and note it, with the date/time, for your installer.
- Check any room thermostat/controller display is lit and its batteries (if battery-powered) are not flat; check thermostat and schedule settings.
What the engineer will check
- Follow the service-manual troubleshooting flow chart for this code: check defect of remote control thermistor; check defect of remote control PC board; check defect of indoor PC board (A1P).
Who to ask for: Heat pump installer (Daikin-trained).
Certification: None specific; MCS-certified installer recommended.
What you might notice
Sources
- Service Manual Daikin ALTHERMA HT ERSQ/ERRQ 011-016 AA V1/Y1 + EKHBRD (ESIE09-08C) ↗ · ESIE09-08C · page 158 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026