Verified boiler fault code
Baxi E.00.04 Fault Code (Baxi 200/400/600/800 and Assure 500 Combi/System common-code group)
Return temperature sensor disconnected.
Safety disclaimer
Fault code summary
- Manufacturer
- Baxi
- Fault code
- E.00.04
- Fault type
- Temperature sensor, Central heating, Electrical
- Severity
- Not specified
- Reset
- Not specified
- Applicable models
- Baxi 200 Combi, Baxi 400 Combi, Baxi 600 Combi, Baxi 800 Combi, Baxi Assure 500 Combi, Baxi 600 System, Baxi 800 System, Baxi Assure 500 System
Quick answer
Return temperature sensor disconnected.
What does this fault code mean?
Return temperature sensor disconnected.
Common causes
- Return temperature sensor disconnected.
Symptoms
This information was not provided in the verified manufacturer source.
What can the homeowner safely check?
This information was not provided in the verified manufacturer source.
Boiler reset information
Reset information was not provided in the verified manufacturer source. Do not repeatedly reset an unresolved fault.
When should I call an engineer?
Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.
Engineer diagnosis
- Check the return temperature sensor and its connection.
Applicable boiler models
Related fault codes
- A.02.06 — Baxi 200/400/600/800 and Assure 500 Combi/System common-code group
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Maximum flow temperature exceeded or flow temperature sensor short-circuited.
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Burner failed to ignite after four attempts.
Read fault code - E.04.12 — Baxi 200/400/600/800 and Assure 500 Combi/System common-code group
Ignition failure — flame monitoring.
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Fan impeller blocked or maximum RPM exceeded.
Read fault code
Manufacturer documentation
Baxi Error CodesE.00.04 | Return temperature sensor disconnected.
Last verified
2026-09-12
Frequently asked questions
What does Baxi E.00.04 mean?
Return temperature sensor disconnected.