Ideal uP fault codewhat it means and how to fix it
A new or reset control board waiting to be programmed. Ideal's manual shows uP as the first thing a replacement PCB displays, before F9, until the installer tells it what boiler it is in.
Take care
Get a Gas Safe registered engineer to look at your Ideal uP
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 uP means
uP is not in any fault table, but people see it and search for it, and Ideal document exactly what it is. In the PCB replacement procedure for the Logic ESP1, step ten reads: turn power on, display shows uP; rotate all three dials fully anticlockwise; press Restart, display shows oF; turn power off; turn power on, display shows F9. From there the installer uses the central heating knob to dial in C for combi, n for natural gas and the boiler size, pressing Restart after each, until the display shows the configuration and one final Restart programmes the board.
So a boiler showing uP is at the very start of that sequence — a board that has never been configured, or one that has lost its configuration and reverted. It will not heat anything in this state. If you are seeing it on a boiler that has just had a PCB fitted, the job was not finished; if you are seeing it on a boiler nobody has touched, the board has failed in a way that wiped it.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Replacement PCB fitted and not programmed | The engineer fitted the board, saw the display light up and left, or was interrupted before the dial-in sequence. This is where Ideal's own procedure says a new board starts. | Common |
| Board reverted to factory state | A PCB whose stored configuration has been lost behaves like a new one. It is uncommon, and the board is usually replaced rather than reprogrammed because whatever wiped it will do so again. | Occasional |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£60–£380
Time on site
30 minutes
Finishing an unprogrammed board is a short visit, £60–£90, and arguably the original engineer's to make at no charge. A failed board replaced and programmed £250–£380.
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.
Ideal Logic primary PCB
£150–£320Authorised Ideal parts distributor
Price checked 28 September 2026
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Related Ideal fault codes
- F9Get it checkedThe control board has not been told what boiler it is in, or has failed. L9 is the same fault locked out. The 2011 Logic Combi row also covers a gas valve short circuit.Related: electronics and power
- dUUsually simple to fixNot a fault. The diverter valve has been parked in its mid-position for servicing and the boiler is waiting to be told the service is over. Ideal publish the way out.Related: electronics and power
- Blank displayGet it checkedNothing on the screen at all. Ideal's user guides send you to the boiler's switch and the consumer unit first; the installer charts then work from the terminal block to the board.Related: electronics and power
- F7Get it checkedThe mains voltage reaching the boiler has dropped below what the board will run on. Ideal's advice is an electrician or your electricity supplier, not a heating engineer.Related: electronics and power
- C0Get it checkedThe board cannot activate the Boiler Chip Card that tells it what model it is fitted to. Ideal's engineer check is whether the small plastic card is in its slot at all.Related: electronics and power
- L9Get it checkedOn a Logic, L9 is the locked-out form of the unconfigured-board fault F9. On an Isar HE it is something else entirely: a heat exchanger overheat read by the dry-fire thermistor.Related: electronics and power
Own an Ideal boiler? Save it and its codes come first next time.
Related guides
Common questions about Ideal uP
The manual prints the programming steps. Why can I not do them?
Because the steps include telling the board the boiler's gas type and output, and Ideal print in capitals that setting the correct size is critical to safe operation. The board sets the gas rate from it. This is Gas Safe work and the installation manual is written for the engineer, not the householder.
Is uP the same as F9?
They are stages of the same condition. uP is the board before configuration begins; F9 is what it shows part-way through, and what it shows if configuration is abandoned there. Both mean the PCB does not yet know what it is driving.
What is oF?
The step after uP in Ideal's sequence: with all three dials turned fully anticlockwise, pressing Restart shows oF, and the board is then powered off and on to reach F9. You would only see it during programming.
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.