E86 Boiler Fault Code: What It Means on Every Brand

The E86 fault code appears on 2 brands — Baxi and Potterton — and it does not mean the same thing on each. The same two or three characters can signal a pressure problem on one boiler and an ignition fault on another, so identify your brand first and use the table below to jump to the right page.

Up to: Lockout — engineer likely 2 brands use this code Meaning differs by brand

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 E86 means	Severity	DIY?
BBaxi	The E86 code appears on Baxi boilers when one internal component has lost the ability to communicate with another — essentially, part of the boiler's electronics has stopped 'talking' to… Full guide →	Lockout — engineer likely	No
PPotterton	The E86 code on a Potterton boiler signals a communication fault — meaning one or more components inside the boiler have lost the ability to exchange data correctly via the PCB (Printed… Full guide →	Engineer may be needed	No

E86 brand by brand

Baxi E86

The E86 code appears on Baxi boilers when one internal component has lost the ability to communicate with another — essentially, part of the boiler's electronics has stopped 'talking' to the rest of the system. Baxi uses a family of closely related codes (E83, E84, E85, E86, and E87) to flag these internal communication breakdowns; E86 is one specific variant within that group. When this handshake between components fails, the boiler locks out as a safety precaution rather than continuing to operate in an unknown state. The fault is almost always electrical in nature — a wiring problem, a loose connector, or a failing PCB — and it requires investigation inside the boiler casing to resolve fully.

Causes, fixes & costs for Baxi E86 → · All Baxi codes

Potterton E86

The E86 code on a Potterton boiler signals a communication fault — meaning one or more components inside the boiler have lost the ability to exchange data correctly via the PCB (Printed Circuit Board). Potterton groups several related codes together in this area: E83, E84, E85, E86, and E87 all sit within the same communication-error family. Depending on your specific model, E86 (and its neighbours) can point to a breakdown in signalling from an NTC temperature sensor, a wiring connection failure, or a loss of communication with a connected room controller or wireless thermostat. Because the PCB acts as the central hub through which every component talks to the rest of the boiler, any broken link in that chain — whether it's a sensor, a wire, or the board itself — can trigger this code. Potterton's Promax, Assure, and Gold/Titanium ranges may interpret these codes slightly differently, so always cross-reference with your model's documentation if you are unsure.

Causes, fixes & costs for Potterton E86 → · All Potterton codes

Frequently asked questions

Is the E86 fault code the same on every boiler?

No. E86 means different things on different brands — see the table above. Always identify your boiler's brand (it is printed on the front casing) before acting on any advice about the code.

Can I fix a E86 fault myself?

Not usually. On every brand listed, E86 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 E86 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.