Medium
E01-603 on Worcester Bosch 28i RSF

Your boiler is detecting an issue with the internal water pressure management, usually caused by a drop in pressure or a flat expansion vessel.

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

Expansion Vessel

From this model's manual
Verified against the Worcester Bosch/Worcester Bosch 28 Rsf 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 the boiler pressure gauge to see if it has dropped below 1 bar.Use the filling loop to top up the boiler pressure until it reads between 1 and 1.5 bar.Reset the boiler to see if the fault clears.

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Related fault codes

EAView →CE211View →D1View →

All 22 fault codes on the 28i RSF

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

E01-058E01-059E01-598E01-599E01-600E01-601E01-602E01-605E01-607E01-610E01-612E01-892E01-900E01-930E01-943E01-944E01-945E01-946E04-582E05-341E58-079

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