Medium
J on Baxi Ecoblue18 System ErP

Your boiler has detected trapped air in the system or a problem with the temperature sensor, causing it to temporarily pause heating for safety.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

System air / Flow temperature sensor issues

From this model's manual
Verified against the Baxi/Baxi Wb Baxi Baxi Ecoblue System Installation And Service M 2 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check your system water pressure gauge and top it up to about 1 bar using the filling loop if it is too low.Bleed your radiators starting from the bottom of the house to the top to release any trapped air.Reset your boiler using the reset button to see if the fault clears.

Find a Gas Safe engineer
Search the official register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like J: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

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

Related fault codes

HView →E119View →E133View →

All 28 fault codes on the Ecoblue18 System ErP

Seeing a different code? Every code this model can display, in one place.

202840109 R110 R111 R117118125 R128130133133 R151 R160 R321384BCDEE118FGHIK

Related guides you might find useful

How to bleed a radiator

Quarter turn on the valve, wait for water, then check the boiler pressure.

Read →

Banging, kettling or whistling noise

Each noise points to a different fault.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →