The Baxi A.02.37 code means “Passive functional device disconnected.” The boiler’s configured control system expects a passive functional device but is not detecting it. Baxi’s public fault table does not identify that device, so it would be unsafe to guess which sensor, accessory or connection is involved.
Write down the exact code and full boiler model, then note whether heating and hot water still work. Keep the boiler closed and avoid technical settings. A persistent A.02.37 message should be investigated by a suitably qualified engineer.
What does Baxi A.02.37 mean?
Baxi lists A.02.37 as a passive functional device disconnected for its current Combi 2 and System 2 model group. The word “passive” is part of the manufacturer’s technical description; it does not mean that the device is unimportant, optional or safe to ignore.
At homeowner level, the useful point is that an expected element is no longer being recognised. The public description does not explain the device’s identity, location or method of connection, and it does not state that the device itself is defective.
How is A.02.37 different from A.02.36?
The codes look similar but Baxi gives them different wording. A.02.36 is “Functional device disconnected,” while A.02.37 is “Passive functional device disconnected.” Record the final digit carefully because it helps the engineer follow the correct technical information.
Do not treat either description as permission to inspect connections yourself. The distinction is for model-specific fault-finding by a competent engineer.
Which boilers use the A.02.37 code?
Baxi’s current list includes Baxi 200, 400, 600 and 800 Combi 2 boilers, Baxi Assure 500 Combi 2, Baxi 600 and 800 System 2, and Baxi Assure 500 System 2. Similar code numbers on older or different ranges may not mean the same thing.
Find your full model from paperwork or an accessible external label. Do not remove any boiler panels to look for model or device information.
What can cause the disconnected message?
The code tells you what the boiler has detected, not why it happened. It may appear after installation or commissioning, following control-related work, after a power interruption, or when part of the expected arrangement is no longer being recognised. Those are possible circumstances, not confirmed causes.
Only trained checks can determine whether the relevant issue is a device, connection, power supply, configuration or another part of the system. A.02.37 does not prove that a specific sensor or control must be replaced.
What can you safely check?
Useful homeowner observations are limited but valuable:
- Confirm the display says A.02.37, not A.02.36 or another similar code.
- Photograph the code and any additional message.
- Record the complete boiler model.
- Note whether heating, hot water or both are affected.
- Check only normal external controls described in the user guide.
- Note any recent installation, service, electrical work or power cut.
Do not start moving or unplugging external controls. The code does not identify the device, and disturbing the system can make the original problem harder to trace.
Can you reset Baxi A.02.37?
If the official guide for your exact boiler explains the normal homeowner reset, you may try it once. A temporary interruption may clear, but a message that remains or returns needs professional attention.
Do not perform a factory reset, enter installer menus or alter configuration parameters. Those actions can change the expected control arrangement without repairing the reason for the disconnection.
What should you not do?
Do not open the casing, inspect internal plugs, test voltage or resistance, bridge terminals, change pairing or work on the boiler PCB. Do not order parts from the code alone. The public wording deliberately does not name a component.
Leave the appliance in a safe condition and preserve the display information for the engineer. Repeated resets and experimental changes can remove useful fault history.
Is A.02.37 a safety warning?
Baxi describes A.02.37 as a disconnected passive functional device rather than a gas-leak warning. Even so, a persistent technical message should not be bypassed, and the boiler should not be dismantled.
If you smell gas, suspect carbon monoxide, feel unwell near the boiler or a carbon-monoxide alarm sounds, leave the property and follow current emergency guidance immediately.
Who can fix Baxi A.02.37?
A suitably qualified Gas Safe registered engineer should investigate. They can use the exact model and installed control arrangement to identify what the boiler expects, carry out safe checks and complete the appropriate repair. Tell them when the code first appeared and whether any recent work came before it.
Want the A.02.37 fault dealt with?
Book a fixed-price boiler repair aimed at fixing the fault, with the booking price clear before the visit.
Quick answers about Baxi A.02.37
What does A.02.37 mean?
Baxi defines it as “Passive functional device disconnected.” An expected part of the configured control arrangement is not being detected.
What does passive device mean?
It is Baxi’s technical category. The public fault table does not define or identify the particular device involved.
Is A.02.37 the same as A.02.36?
No. Baxi lists A.02.36 as functional device disconnected and A.02.37 as passive functional device disconnected.
Can I check the wiring?
No. Keep the boiler closed and do not test, bridge or reconnect wiring or terminals.
Will a reset fix it?
One model-approved reset may clear a temporary interruption. If the message returns, arrange a repair.
Does the code prove a sensor has failed?
No. The code does not name the device or prove that a particular part is defective.