EF on a Worcester Bosch Greenstar Plus Hybrid: System fault appliance PCB / basic controller (status L); hybrid control module component fault; EEPROM error in hybrid control module (display blank)
Short answer
On a Worcester Bosch heat pump, EF means: System fault appliance PCB / basic controller (status L); hybrid control module component fault; EEPROM error in hybrid control module (display blank). 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 manuals for this range word it in different ways:
- System fault appliance PCB / basic controller (status L); hybrid control module component fault; EEPROM error in hybrid control module (display blank).
- Unknown fault.
Part involved: hybrid control module / FW200; internal-external unit communication.
When it shows: System fault appliance PCB / basic controller (status L); hybrid control module component fault; EEPROM error in hybrid control module (display blank) Unknown fault.
Likely causes:
- Contact problem between appliance PCB/base controller; hybrid control module component fault; EEPROM error - check/replace hybrid control module.
- No detailed cause given in Table 39 (listed in Table 38 only).
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.
- Read and note the full FW200/hybrid manager fault code shown on the controller and pass it to your installer.
- Check the heat pump isolator and consumer-unit breaker(s) are switched on; if a breaker has tripped more than once, leave it off and call an engineer.
- Check the outdoor unit is not blocked by leaves, snow, ice or other debris (do not open the casing).
What the engineer will check
- Contact problem between appliance PCB/base controller; hybrid control module component fault; EEPROM error - check/replace hybrid control module.
- Diagnose with service tool 7-716-161-051.
Who to ask for: Gas Safe registered engineer + heat pump installer; heat pump installer / electrician.
Certification: Gas Safe registration for any work on the boiler; F-gas for refrigerant circuit; 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) · pages 58, 61 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026