Potterton E09 fault codewhat it means and how to fix it
The Assure and Promax Ultra's gas valve connection cable fault: the board has lost its wiring link to the valve. Resettable once; recurring 09 is a wiring or PCB job.
Take care
Has the boiler been worked on recently?
The right answer depends on what you can see. Pick the one that matches.
Choose the option on the left that matches what your appliance is doing, and the answer for that case appears here.
Yes — service or repair in the last few weeks
Very likely a connector not pushed home.
Ask the same engineer back; it is a two-minute check.
No
Lead or board.
Engineer.
What E09 means
The first row of the Assure and Promax Ultra tables is "09 — Gas valve connection cable". It is a wiring fault by name: the lead between the PCB and the gas valve is open, shorted or unplugged, and the board reports it before it tries to light. Both installation manuals include 09 among the nine codes a one-to-three-second press of Reset may clear, and their fault-finding chart gives it a specific footnote shared with 15, 110 and 384: when any of the four flashes or keeps returning, every connection on the PCB is to be checked and, failing that, the PCB replaced.
The Promax, Titanium and Gold tables do not contain it; the older boards had no separate code for the valve lead and would have shown E133 when ignition failed. The Assure Combi user guide shows 09 with an R, so the owner is permitted the one press. After that it is an engineer's look at the connector on the valve and the plug on the board, which is quick, and then the board itself, which is not cheap.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Connector off or loose at the gas valve or PCB | The lead is disturbed at services and when the valve is changed. A plug not fully home is the common finding. | Common |
| Damaged lead | Chafed or heat-damaged insulation on the valve harness, or a broken core at the crimp. | Occasional |
| PCB | The manual's last step for a recurring 09: replace the PCB. | Occasional |
What to try yourself
Press Reset for about a second.
If 09 returns, leave it and contact your installer or Baxi Customer Support. The fault is inside the casing and the checks are electrical.
Get a Gas Safe registered engineer to look at your Potterton E09
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 it costs to fix
Typical repair cost
£0–£320
Time on site
5 minutes
Connector reseated at a call-out £60–£90. Harness £40–£90. PCB £220–£320.
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 Potterton fault codes
- E133Get it checkedGas supply interrupted, ignition failed or no flame detected — every Potterton generation. Confirm the gas supply, one reset (5 s on the knob, 1–3 s on the button), and call if it returns.Related: ignition and gas supply
- E128Get it checkedFlame failure during normal operation on the Potterton Assure and Promax Ultra: the burner was lit and went out. Resettable; recurring E128 wants an engineer.Related: ignition and gas supply
- E135Get it checkedThe Assure and Promax Ultra's internal-error ignition code: the control blames its own side of the gas valve rather than the supply for the flame that never came. One reset; then an engineer.Related: ignition and gas supply
- Red light flashingGet it checkedPotterton Assure Heat, Titanium Heat and Ultra Heat have no display: the illuminated button flashes red a number of times when the boiler has locked out. The count is the code.Related: ignition and gas supply
- E15Get it checkedThe Assure and Promax Ultra's own-valve code: the board has detected a fault in the gas valve itself, not its cable. One reset allowed; then an engineer with a meter.Related: ignition and gas supply
- E384Get it checkedThe Assure and Promax Ultra report a flame signal while the gas valve is shut. An electrode or PCB fault, and the Assure manual's answer is to go over the board.Related: ignition and gas supply
Own a Potterton 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
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.