E168 Boiler Fault Code: What It Means on Every Brand

E168 is the Baxi platform's catch-all lockout, seen on Baxi, Potterton and Main: the board detected an internal or electrical anomaly it cannot attribute to a specific component — engineers sometimes call it the 'mystery code'. A single power-cycle clears a transient; a recurring E168 usually points at the control board or its supply.

Lockout — engineer likely 3 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 E168 means	Severity	DIY?
BBaxi	The E168 fault code on Baxi boilers signals that the boiler's control board has detected an internal electrical problem and has shut the unit down as a safety measure. Full guide →	Lockout — engineer likely	No
MMain	The E168 is Main's catch-all lockout code — sometimes called the 'mystery code' — because it doesn't point to a single specific component. Full guide →	Lockout — engineer likely	No
PPotterton	The E168 code appears on Potterton boilers when the appliance has entered a lockout state — meaning it has shut itself down to prevent unsafe operation or further damage. Full guide →	Lockout — engineer likely	No

E168 brand by brand

Baxi E168

The E168 fault code on Baxi boilers signals that the boiler's control board has detected an internal electrical problem and has shut the unit down as a safety measure. It acts as a broad catch-all alert rather than pinpointing one specific component — the boiler has sensed something is wrong but cannot always identify the precise root cause. On certain models such as the 600 Series and Megaflo range, E168 is linked specifically to a temperature sensor fault, while on Duo-tec models it is more commonly associated with a PCB voltage error or ignition lockout. The boiler will not restart until the underlying fault is resolved and the error is cleared.

Causes, fixes & costs for Baxi E168 → · All Baxi codes

Main E168

The E168 is Main's catch-all lockout code — sometimes called the 'mystery code' — because it doesn't point to a single specific component. Instead, it signals that the boiler's PCB has shut the appliance down after detecting a problem it cannot clearly categorise. In practice, E168 most often appears after a failed ignition sequence (the boiler tried to light the burner several times but the ionisation probe never confirmed a stable flame), after mains voltage fluctuated outside the acceptable ±10% of 230 V, or as a residual code left behind when an earlier fault (such as E119 low pressure or E133 ignition failure) was cleared by a reset without the underlying issue being resolved. Because E168 is shared across the Main, Baxi, and Potterton ranges from the same manufacturer group, guidance for one brand applies equally to the others. The boiler will not provide heating or hot water while this code is active.

Causes, fixes & costs for Main E168 → · All Main codes

Potterton E168

The E168 code appears on Potterton boilers when the appliance has entered a lockout state — meaning it has shut itself down to prevent unsafe operation or further damage. Rather than pointing to one specific component failure, E168 is a broad safety-shutdown signal that can follow an unresolved prior fault, a disrupted power supply, an ignition failure, or an internal component problem. Because the boiler's PCB (Printed Circuit Board) is responsible for triggering this lockout, E168 is sometimes referred to as a PCB lockout code, though the root cause is often elsewhere in the system. The same code appears on compatible Baxi and Main boilers that share the same platform.

Causes, fixes & costs for Potterton E168 → · All Potterton codes

Frequently asked questions

Is the E168 fault code the same on every boiler?

Broadly, yes — on Baxi, Main and Potterton the E168 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 E168 fault myself?

Not usually. On every brand listed, E168 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 E168 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.