Biasi E01 Fault Code: Causes, Fixes & Repair Costs
What does the Biasi E01 fault code mean?
The Biasi E01 (also displayed as ER 01 on older models such as the Riva Plus and Garda, or E133 on newer Inovia and Advance Plus models) indicates that the boiler has failed to ignite and has locked itself out as a safety measure. Essentially, the burner attempted to light but could not establish or sustain a flame, so the boiler has shut down to prevent unburned gas from accumulating. Depending on the model, this code can also flag a low system pressure condition, since some Biasi control boards will refuse to attempt ignition if pressure has dropped too far. In either case, the boiler will not produce heat or hot water until the underlying problem is resolved and the unit is reset.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. 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.
Common causes
- Blocked or dirty burner jets Common
Over time, debris and combustion residue can partially or fully clog the small holes in the burner, restricting the flow of gas and preventing a stable flame from forming. This is one of the most frequent reasons a Biasi boiler throws an ignition lockout, particularly on units that have not been serviced recently.
- Gas supply issue Common
If the gas meter isolation valve is partially closed, the gas supply pressure from the network is temporarily low, or a prepayment meter has run out of credit, the boiler simply won't have enough gas to light. Checking whether other gas appliances in the home — cooker, gas fire — are working normally helps to rule this in or out quickly.
- Low system pressure Common
Some Biasi models will display E01 when boiler circuit pressure drops below the minimum threshold (typically around 0.5 bar). The boiler's protection logic prevents ignition attempts when pressure is insufficient. Reading the pressure gauge on the front panel will confirm whether this is the cause.
- Fan fault or incorrect fan speed Sometimes
The boiler's PCB will not trigger ignition unless it first receives confirmation that the flue fan is running correctly — this ensures combustion gases can safely escape. A fan that is partially seized, running at the wrong speed, or has failed entirely will cause the board to abort the ignition sequence and lock out.
- Faulty or incorrectly wired gas valve Sometimes
The gas valve is the component that physically allows gas into the burner. If its wiring harness is damaged, corroded, or has a loose connection, the valve may not open on command even though the rest of the ignition sequence runs normally. A faulty valve itself — one that is stuck or has a failed solenoid — produces the same result.
- PCB fault Rare
The printed circuit board orchestrates the entire ignition sequence. A failing PCB may send incorrect signals to the igniter, gas valve, or fan, or it may misread sensor data and abort ignition unnecessarily. PCB faults are less common but should be considered once other causes have been ruled out, as replacement is one of the more costly repairs.
How to fix it
- Reset the boiler once DIY safe
Locate the reset button on the Biasi's front control panel, press and hold it for approximately 5–10 seconds until the display changes and the boiler attempts to restart. Allow up to 10 minutes for the full ignition sequence to complete. If the boiler fires up and runs normally, monitor it over the next day or two. Do not reset more than two or three times in total — repeated failed ignition attempts can allow unburned gas to build up in the combustion chamber, which is a safety hazard.
- Check your gas supply DIY safe
Turn on another gas appliance in your home — a gas hob burner is the simplest test. If that also fails to light or the flame is very weak, the problem lies with the gas supply rather than the boiler itself. Contact your gas supplier or check your meter (including credit on a prepayment meter) before proceeding further.
- Check and top up boiler system pressure DIY safe
Look at the pressure gauge on the boiler's front panel. The needle should sit between 1.0 and 1.5 bar when the system is cold. If it reads below 1.0 bar, use the filling loop (usually a braided flexible hose or inline lever beneath the boiler) to slowly admit mains water until the gauge reaches around 1.2–1.5 bar, then close the loop valve firmly. Reset the boiler again. If pressure drops again within a few days, there is a leak in the system that needs professional attention.
- Check the condensate pipe for a blockage DIY safe
In cold weather, the plastic condensate drain pipe — which typically runs to an external drain or soakaway — can freeze solid, causing the boiler to lock out. If the pipe feels solid or you can see ice, gently warm the outside section with warm (not boiling) water or a hot-water bottle. Once thawed, reset the boiler.
- Call a Gas Safe registered engineer if the fault persists Gas Safe engineer
If E01 / ER 01 returns after your reset attempts, or if you are unable to identify a simple cause such as low pressure or a frozen condensate pipe, you need a Gas Safe registered engineer. They will carry out a full ignition diagnosis: testing gas inlet pressure at the valve, inspecting and cleaning the burner jets, checking the fan speed and pressure differential switch, testing the gas valve solenoids and wiring harness with a multimeter, and assessing the PCB. Do not attempt to access gas components, the gas valve, or the PCB yourself.
Parts you may need
- Biasi gas valve · from £150
- Biasi burner assembly / jet kit · from £55
- Biasi flue fan (combustion fan) · from £110
- Biasi PCB (main control board) · from £180
- Air pressure switch · from £45
- Ignition electrode / lead set · from £30
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–£380, depending on the underlying cause.
Frequently asked questions
What is the difference between E01, ER 01, and E133 on a Biasi boiler?
These are all the same underlying fault presented differently depending on the age and model of your boiler. Older Biasi boilers such as the Riva Plus and Garda use the ER 01 display format. Mid-range models tend to show E01. Newer units in the Inovia and Advance Plus ranges may display E133 instead. In every case, the boiler is telling you it has failed to achieve ignition and has locked out — the diagnostic steps and likely causes are identical regardless of which variant you see on screen.
Can I keep resetting my Biasi boiler to clear E01?
You can try one or two resets to see whether the fault clears on its own — occasionally a temporary glitch in the gas supply or a brief pressure dip can cause a one-off lockout. However, repeatedly resetting without fixing the underlying fault is not a solution and can be counterproductive. Each failed ignition attempt introduces a small amount of unburned gas into the combustion chamber. If the code keeps coming back, stop resetting and call a Gas Safe engineer to find the root cause.
How much does it typically cost to fix a Biasi E01 fault in the UK?
Most homeowners with this fault end up paying somewhere between £100 and £380 all in, depending on what needs doing. A straightforward call-out to clean blocked burner jets or top up pressure might come to £100–£150 including labour. Fan replacement typically costs around £220–£280 with parts and labour, and a gas valve replacement is usually in the region of £280–£350. PCB replacement can be more expensive — sometimes £350–£500 — and on an older boiler it may be worth comparing that cost against a new boiler quote.
Is the Biasi E01 fault dangerous?
The boiler has locked out specifically to keep you safe — it is not producing heat or releasing gas into your home during a lockout. You should not smell gas; if you do, do not reset the boiler, leave the property, ventilate if possible, and call the National Gas Emergency Service on 0800 111 999 immediately. Assuming there is no gas smell, the E01 code itself represents a stopped boiler rather than an active hazard, but the fault should still be diagnosed and fixed promptly by a Gas Safe engineer rather than masked with repeated resets.