E06 Boiler Fault Code: What It Means on Every Brand

The E06 fault code appears on 3 boiler brands — Biasi, Ravenheat and Warmflow — 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.

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 E06 means	Severity	DIY?
BBiasi	The E06 (sometimes displayed as ER 06) fault code on Biasi boilers indicates that the central heating flow temperature sensor — known as the NTC (Negative Temperature Coefficient) probe —… Full guide →	Lockout — engineer likely	No
RRavenheat	The E06 code on a Ravenheat boiler indicates that the central heating flow temperature sensor has detected an excessively high reading, causing the boiler to lock itself out as a safety… Full guide →	Lockout — engineer likely	No
WWarmflow	The E06 code on a Warmflow boiler indicates a fault with the Domestic Hot Water (DHW) Flow NTC Temperature Sensor. Full guide →	Lockout — engineer likely	No

E06 brand by brand

Biasi E06

The E06 (sometimes displayed as ER 06) fault code on Biasi boilers indicates that the central heating flow temperature sensor — known as the NTC (Negative Temperature Coefficient) probe — has either failed or is sending readings the boiler's control board considers implausible. This sensor monitors the temperature of water leaving the heat exchanger on its way to your radiators. When it stops working correctly, the boiler can no longer regulate heating safely, so it shuts down and locks out. You will need to reset the boiler to clear the lockout, but unless the underlying problem is resolved the fault will almost certainly return shortly afterwards. A Gas Safe registered engineer is required to diagnose and repair this fault properly.

Causes, fixes & costs for Biasi E06 → · All Biasi codes

Ravenheat E06

The E06 code on a Ravenheat boiler indicates that the central heating flow temperature sensor has detected an excessively high reading, causing the boiler to lock itself out as a safety measure. The sensor responsible is an NTC (Negative Temperature Coefficient) thermistor — a small heat-sensitive resistor mounted on the pipework that continuously reports water temperature to the PCB. When that reading climbs beyond safe limits, the boiler shuts down to protect itself and your home. The lockout will persist until the underlying cause is resolved; repeated resets without fixing the root problem will not clear it permanently.

Causes, fixes & costs for Ravenheat E06 → · All Ravenheat codes

Warmflow E06

The E06 code on a Warmflow boiler indicates a fault with the Domestic Hot Water (DHW) Flow NTC Temperature Sensor. This small thermistor monitors the temperature of water flowing through the hot water circuit and feeds that reading back to the boiler's control board. Because its resistance changes predictably as temperature rises or falls, the PCB relies on it to regulate DHW delivery safely. When the boiler detects a short circuit in the sensor circuit, an open circuit (disconnected sensor), or a reading that falls outside the expected range, it locks out and displays E06. Without a trustworthy signal from this sensor, the boiler cannot safely heat domestic hot water, so it shuts down as a precaution.

Causes, fixes & costs for Warmflow E06 → · All Warmflow codes

Frequently asked questions

Is the E06 fault code the same on every boiler?

Broadly, yes — on Biasi, Ravenheat and Warmflow the E06 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 E06 fault myself?

Not usually. On every brand listed, E06 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 E06 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.