Biasi ER06 Fault Code: Central Heating NTC Temperature Probe Fault
The ER06 fault code on a Biasi boiler points to a problem with the central heating (CH) NTC temperature probe — the sensor that monitors the temperature of water flowing through your heating circuit. When the probe sends readings outside the expected range, or stops sending readings altogether, the boiler's PCB interprets this as a safety risk and shuts the boiler down in a lockout state. You will need to identify and fix the underlying cause before the boiler will operate again. Note: a small number of sources describe ER06 as a burner ignition fault; however, the manufacturer-referenced fault index clearly defines it as a heating temperature sensor fault, and this is the interpretation supported by the majority of specialist sources.
General guidance only — not a substitute for professional advice. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
What does the Biasi ER06 fault code mean?
The ER06 fault code on a Biasi boiler points to a problem with the central heating (CH) NTC temperature probe — the sensor that monitors the temperature of water flowing through your heating circuit. When the probe sends readings outside the expected range, or stops sending readings altogether, the boiler's PCB interprets this as a safety risk and shuts the boiler down in a lockout state. You will need to identify and fix the underlying cause before the boiler will operate again. Note: a small number of sources describe ER06 as a burner ignition fault; however, the manufacturer-referenced fault index clearly defines it as a heating temperature sensor fault, and this is the interpretation supported by the majority of specialist sources.
Common causes
- Faulty or failing NTC temperature probe Common
The CH NTC probe measures the flow temperature of the central heating water. If the probe has developed a fault — whether through age, damage, or a wiring issue — it will feed inaccurate or absent data back to the PCB. The PCB then assumes the system is operating outside safe limits and triggers a lockout. This is the most common root cause of ER06.
- Circulation pump fault or blockage Common
If the pump is not moving water around the system properly — due to a blockage from sludge or limescale, being set to the wrong speed, or a mechanical or electrical failure — heat can build up around the heat exchanger. The NTC probe detects this abnormal temperature behaviour and the boiler locks out with ER06. The pump can sometimes seize after a long idle period such as summer months.
- Air in the heating system Sometimes
An airlock in the central heating circuit can restrict water flow, causing localised temperature spikes or drops that the NTC probe picks up as abnormal. Bleeding radiators throughout the system can remove trapped air and, once resolved, a boiler reset may clear the fault.
- Wiring or connector issues at the probe Sometimes
Loose terminals, corroded connectors, or damaged wiring between the NTC probe and the PCB can cause intermittent or incorrect signals. The PCB cannot distinguish this from a genuinely faulty probe and will lock the boiler out in the same way.
- PCB fault Rare
If the PCB itself is malfunctioning — perhaps due to water ingress from a leaking pump seal or a component failure — it may misread or fail to read the NTC probe signal even when the probe is perfectly healthy. This is a less common cause and is usually only confirmed after other components have been ruled out.
How to fix it
- Attempt a single boiler reset DIY safe
Press the reset button on your Biasi boiler and wait for it to restart. If the boiler fires up and runs normally, monitor it over the next hour or so. If ER06 returns promptly, do not keep resetting — repeated resets without fixing the underlying fault will not help and may mask useful diagnostic information for the engineer. Limit resets to two or three attempts at most.
- Bleed your radiators to clear any airlocks DIY safe
Turn off the boiler and allow it to cool. Using a radiator bleed key, open the bleed valve on each radiator (starting from the ground floor and working upwards) until water flows steadily with no air spluttering out. Once all radiators are bled, check and top up system pressure to around 1–1.5 bar using the filling loop if it has dropped, then attempt a reset. If the fault clears and the boiler runs normally, an airlock was likely the culprit.
- Check your system pressure DIY safe
Look at the pressure gauge on your boiler. It should read between 1 and 1.5 bar when the system is cold. If pressure is below 1 bar, top it up via the filling loop (a pair of braided hoses under the boiler with small valves — open both slowly until the gauge reaches the correct level, then close them). Low pressure alone can sometimes contribute to circulation problems that trigger ER06.
- Arrange for a Gas Safe engineer to test the NTC probe Gas Safe engineer
A qualified engineer will use a multimeter to check the resistance of the CH NTC temperature probe against its expected values at a given temperature. If the probe is reading incorrectly or showing an open or short circuit, it will need to be replaced. This is not a gas component, but working inside the boiler casing should only be carried out by a competent registered engineer.
- Have the engineer inspect and test the circulation pump Gas Safe engineer
The engineer will check whether the pump is running, confirm it is set to the correct speed, and assess whether it is moving water effectively. Sludge or limescale build-up can be treated with a chemical flush, and a seized or failed pump will need to be replaced. A powerflush of the whole system may be recommended if heavy contamination is found.
- Have the engineer inspect PCB wiring and connections Gas Safe engineer
The engineer will check all electrical connections to and from the NTC probe for signs of corrosion, looseness, or damage. In some cases simply re-seating a connector resolves the fault. If the PCB itself is found to be faulty — particularly if water ingress is evident — it will need to be replaced.
- Reset the boiler after the repair is completed DIY safe
Once the engineer has completed the repair, a full boiler reset is required to clear the ER06 lockout. Follow the engineer's instruction or your boiler manual for the correct reset procedure. Do not reset the boiler before the fault has been addressed.
Parts you may need
- CH NTC temperature probe (Biasi compatible) · from £25
- Circulation pump (Biasi compatible) · from £85
- PCB (Biasi model-specific) · from £180
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £100–£350, depending on the underlying cause.
Frequently asked questions
Can I fix Biasi ER06 myself by just resetting the boiler?
A reset alone will not fix ER06 if there is an underlying fault with the NTC probe, pump, or wiring. The only DIY steps worth trying are bleeding your radiators to remove airlocks and checking your system pressure. If the fault returns after a reset, you need a Gas Safe registered engineer to diagnose and repair the root cause.
How much does it cost to fix a Biasi ER06 fault in the UK?
For most households, the repair bill lands somewhere between £100 and £350. A straightforward NTC probe replacement including labour typically costs around £100–£180, while a pump replacement usually comes in at £200–£300 all in. If the PCB turns out to be the problem, costs rise significantly — a replacement PCB and labour can reach £400–£500 or more. If your boiler is older and facing a PCB replacement, it is worth getting a new boiler quote at the same time for comparison.
Could ER06 mean a burner ignition fault on some Biasi models?
A small number of sources do describe ER06 as a burner ignition fault. However, the manufacturer's own fault index defines E06 as a heating temperature sensor fault, and this is backed up by the majority of specialist Biasi fault-code references. If bleeding the system and replacing the NTC probe does not resolve the issue, ask your engineer to also check the ignition components in case your specific model uses a slightly different fault code mapping.
My Biasi boiler is still under warranty — what should I do?
Biasi boilers typically carry a warranty of five to seven years depending on the model. If your boiler is within that period, contact Biasi directly before arranging an independent repair, as an unauthorised repair may affect your warranty. Have your model number and installation date to hand when you call.