H.02-.03 Boiler Fault Code: What It Means on Every Brand

The H.02-.03 fault code appears on 2 boiler brands — Baxi and Remeha — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.

Engineer may be needed 2 brands use this code

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What H.02-.03 means	Severity	DIY?
BBaxi	The Baxi H.02.03 fault code indicates a temporary configuration error on the boiler's printed circuit board (PCB). Full guide →	Engineer may be needed	No
RRemehashown as H.02.03	H.02.03 is a temporary blocking fault (the 'H' prefix indicates the boiler has paused rather than permanently locked out) triggered when the boiler's control unit cannot recognise or read… Full guide →	Engineer may be needed	No

H.02-.03 brand by brand

Baxi H.02-.03

The Baxi H.02.03 fault code indicates a temporary configuration error on the boiler's printed circuit board (PCB). Specifically, the control board's C1/C2 (also referred to as CN1/CN2) setup parameters have either not been entered, have been entered incorrectly, or have become corrupted. The boiler cannot operate safely without these settings, as they tell the PCB exactly how it has been configured for your particular system. This type of error most commonly surfaces shortly after a new boiler is installed, after a PCB has been replaced, or occasionally following a power surge. It is a PCB-level setup fault that requires a Gas Safe registered engineer to resolve — there is no homeowner fix beyond attempting a single reset.

Causes, fixes & costs for Baxi H.02-.03 → · All Baxi codes

Remeha H.02.03

H.02.03 is a temporary blocking fault (the 'H' prefix indicates the boiler has paused rather than permanently locked out) triggered when the boiler's control unit cannot recognise or read its own configuration settings. Specifically, the two configuration parameters known as CN1 and CN2 — which tell the control board exactly what appliance it is running on — are either missing, unrecognised, or have become corrupted. Until these values are correctly entered, the boiler will refuse to fire. This is fundamentally a software/settings issue rather than a mechanical breakdown, which is why the boiler itself may be in perfectly good physical condition yet still display this code.

Causes, fixes & costs for Remeha H.02.03 → · All Remeha codes

Frequently asked questions

Is the H.02-.03 fault code the same on every boiler?

Broadly, yes — on Baxi and Remeha the H.02-.03 code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.

Can I fix a H.02-.03 fault myself?

Not usually. On every brand listed, H.02-.03 points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.

Who should I call about a H.02-.03 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.