This fault can involve incomplete combustion and carbon monoxide.
If anyone in the property feels sick, dizzy or drowsy, or you can smell gas: open the windows, leave the building, and do not switch anything on or off. Then call the National Gas Emergency Service.
0800 111 999Baxi E.04.17 fault codewhat it means and how to fix it
Gas valve control circuit fault on the Baxi 200/400 Combi and Combi 2. Baxi's remedy is the main PCB or the air-gas unit, and there is nothing for the householder to try.
Stop — this needs an engineer
Get a Gas Safe registered engineer to look at your Baxi E.04.17
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What E.04.17 means
E.04.17 is "fault in gas valve control circuit" in the Combi 2 manual and on Baxi's professional page, and "problem on the gas valve" in the 200/400 Combi manual, where it is shown as E04 alternating with 17. The board drives the gas valve through a monitored circuit and has found that circuit doing something it should not — no response, the wrong response, or a signal that fails the board's self-check — and it will not run a burner whose gas control it does not trust.
Baxi's remedies point in different directions on the two ranges, which is worth knowing before anyone orders a part. The Combi 2 table gives the cause as "MAIN PCB ERROR — replace the main PCB", and adds a sister code, E.04.54, with the same description and the remedy "check the wiring on the gas valve, replace the gas valve or PCB". The 200/400 table says "defective gas/air unit — replace gas/air unit", the assembly of fan, venturi and valve on that range. Between them they describe the two ends of one circuit, and an engineer will test which end has failed rather than guess.
A related permanent code, E.02.17, "permanent communication failure between gas valve and boiler PCB", and its temporary form H.01.00 describe the same link failing to talk rather than failing to act; the 200/400 manual's remedy for those is "loose connection to gas valve — check gas valve connection from PCB". This page is rated danger because it is a gas control fault. The reset button exists, but Baxi's tables offer no check a householder can make, and a valve the board cannot control is not something to reset repeatedly on the chance it clears.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Main PCB gas valve drive | The Combi 2 table's only entry: "main PCB error — replace the main PCB". The board's valve-drive circuit has failed its self-check. | Common |
| Gas valve or air-gas unit | The 200/400 table's entry: "defective gas/air unit". The valve coil or its internal electronics have failed and the board reads the circuit as wrong. | Common |
| Wiring between board and valve | Named under E.04.54 and E.02.17: "check the wiring on the gas valve", "check gas valve connection from PCB". A plug not fully home or a damaged lead. | Occasional |
| Electromagnetic interference | The Combi 2 table lists "check for any electromagnetic interference" under E.02.17. Rare, but a boiler sharing a cupboard with a large inverter or motor drive can lose the valve link. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£80–£450
Time on site
1 hour
Wiring repair within a call-out. PCB £250–£400 fitted. Air-gas unit on a 200/400 £300–£450.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Baxi / Potterton / Main gas valve
7683968£120–£240Authorised Baxi parts distributor
Price checked 28 September 2026
Baxi / Potterton / Main main PCB
£150–£320Authorised Baxi parts distributor
Price checked 28 September 2026
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Related Baxi fault codes
- E133Get it checkedBaxi's ignition lockout: "the gas supply has been interrupted, ignition has failed or the flame has not been detected". Check the gas is on, reset once. If it returns, stop.Related: ignition and gas supply
- E.04.10Get it checkedIgnition failure on the Baxi 200/400 Combi and every Combi 2: the burner would not light after its allowed attempts. Baxi's own quick guide names it the frozen-condensate code you can fix yourself.Related: ignition and gas supply
- E128Get it checkedFlame failure while the burner was running, on the digital-display Baxis. The boiler relights itself unless it keeps happening; Baxi's manuals name gas supply, electrode and flue as the things to check.Related: ignition and gas supply
- E134Get it checkedBaxi's "elapsed time — gas valve open without gas": the valve opened, nothing arrived. Check the meter and credit before anything else; it resets from the panel.Related: ignition and gas supply
- E.01.04Stop — call an engineer"Flame loss detected five times in 24 hours": the burner keeps lighting and going out on a Baxi 200/400 Combi or Combi 2. Gas pressure, valve calibration, flue or electrode — an engineer's list.Related: ignition and gas supply
- E09Get it checkedGas valve connection cable fault on the 600, 800, Compact and Duo-tec 2. The board cannot talk to the valve. Baxi allow one reset; a repeat means the wiring or the PCB.Related: ignition and gas supply
Own a Baxi boiler? Save it and its codes come first next time.
Related guides
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
- Manufacturer support portal
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.