d1 on a Worcester Bosch Greenstar Plus Hybrid: Return temp. sensor contact faulty (status L) - temperature sensor short/open circuit, condenser inlet
Short answer
On a Worcester Bosch heat pump, d1 means: Return temp. sensor contact faulty (status L) - temperature sensor short/open circuit, condenser inlet. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Return temp. sensor contact faulty (status L) - temperature sensor short/open circuit, condenser inlet.
Part involved: hybrid control module / FW200.
When it shows: Return temp. sensor contact faulty (status L) - temperature sensor short/open circuit, condenser inlet.
Likely causes:
- Condenser inlet sensor short or open circuit; check contacts, wiring, sensor.
Is it safe?
| 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: no.
Manual reset: Hold Back button on hybrid control module 5 s to restart after fault is rectified (installer).
What you can check
- Read and note the full code (and sub-code) shown on the controller and pass it to your installer.
- Check whether the boiler display also shows a fault (manual: if the boiler shows a fault the heat pump is not faulty) and report both to the engineer.
What the engineer will check
- Condenser inlet sensor short or open circuit; check contacts, wiring, sensor.
Who to ask for: heat pump installer / electrician.
Certification: Electrical work to BS 7671 by competent person.
What you might notice
Sources
- Installation and Maintenance Instructions Greenstar Plus Hybrid ↗ · 6 720 803 687 (2012/11) · page 58 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026