Baxi E40 Fault Code (Baxi and legacy Baxi/Main/Potterton ranges listed on common-code page)

Safety disclaimer

Fault code summary

Manufacturer

Baxi

Fault code

E40

Fault type

Central heating, Temperature sensor, Electrical

Severity

Not specified

Reset

Not specified

Applicable models

Baxi Platinum Compact Combi, Baxi Duo-tec Compact Combi, Baxi Megaflo Compact System, Main Eco Compact Combi & System, Baxi 600 Combi & System, Baxi 800 Combi & System, Baxi Duo-tec Combi, Baxi Assure Combi & System, Baxi Platinum + Combi, Potterton Assure Combi & System, Baxi Platinum + Combi, Baxi Megaflo System, Baxi EcoBlue Combi & System

Quick answer

Return central-heating NTC sensor fault — short circuit/open circuit.

What does this fault code mean?

Return central-heating NTC sensor fault — short circuit/open circuit.

Common causes

• Return CH NTC sensor short circuit or open circuit.

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

• Assess the return CH NTC sensor and wiring.

Applicable boiler models

• Baxi Platinum Compact Combi
• Baxi Duo-tec Compact Combi
• Baxi Megaflo Compact System
• Main Eco Compact Combi & System
• Baxi 600 Combi & System
• Baxi 800 Combi & System
• Baxi Duo-tec Combi
• Baxi Assure Combi & System
• Baxi Platinum + Combi
• Potterton Assure Combi & System
• Baxi Platinum + Combi
• Baxi Megaflo System
• Baxi EcoBlue Combi & System

Related fault codes

• E09 — Baxi and legacy Baxi/Main/Potterton ranges listed on common-code page

  Gas-valve connection fault.

  Read fault code
• E110 — Baxi and legacy Baxi/Main/Potterton ranges listed on common-code page

  Boiler maximum temperature exceeded for gradient, or safety thermostat sensor tripped.

  Read fault code
• E118 — Baxi and legacy Baxi/Main/Potterton ranges listed on common-code page

  Water pressure low (below 0.5 bar).

  Read fault code
• E12 — Baxi and legacy Baxi/Main/Potterton ranges listed on common-code page

  Differential water-flow switch fault (still open).

  Read fault code
• E125 — Baxi and legacy Baxi/Main/Potterton ranges listed on common-code page

  Water circulation fault.

  Read fault code
• E128 — Baxi and legacy Baxi/Main/Potterton ranges listed on common-code page

  Safety error for frequent loss of flame.

  Read fault code
• E130 — Baxi and legacy Baxi/Main/Potterton ranges listed on common-code page

  Flue thermostat sensor tripped (lockout).

  Read fault code
• E133 — Baxi and legacy Baxi/Main/Potterton ranges listed on common-code page

  Gas supply fault.

  Read fault code

Manufacturer documentation

E40 | Return central heating NTC sensor fault- short circuit/open circuit.

Last verified

2026-09-12

Frequently asked questions