BoilerFaultCodes.com
1-E3 High Lockout

Your boiler's internal electronic computer chip is either missing, loose, or incompatible with the unit's software.

Call an engineer soon

Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Code plug number: Coding plug number.

What causes this fault?

This fault occurs when the boiler's control system cannot communicate with its 'identity chip,' which tells the unit its specific model and power settings. This usually happens if the chip has vibrated loose from its socket on the main circuit board or if the chip itself has suffered an internal electrical failure. In some cases, a power surge may have corrupted the memory or damaged the printed circuit board where the chip is housed.

Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Protect yourself from future repair bills

A boiler cover plan would cover faults like 1-E3 — no call-out fees, no surprises.

Top rated
OpenFix
Boiler & heating care plans
Get a quote →
Hometree
from £12.95/month
Get a quote →
HomeServe
from £8.00/month
Get a quote →

Affiliate links — we may earn a commission at no extra cost to you.

Could it be time for a new boiler?

If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.

UK's #1 online installer
Boxt
Fixed-price online quotes. Next-day installation.
Get a free quote →
Heatable
Instant online boiler quotes from £1,499.
Get a free quote →
iHeat
Fast installation. Price match guarantee.
Get a free quote →

Affiliate links — we may earn a commission at no extra cost to you.

Related fault codes