Low
S.00 on Vaillant ecoTEC sustain

Your boiler is currently in standby mode because it has not been asked to provide any heating or hot water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Heating mode: No requirement

Shared across the ecoTEC sustain range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s 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 room thermostat or smart controller settingsEnsure the timer or programmer is set to 'On' for the desired time periodTurn up the heating temperature dial on the boiler front panel to test if it kicks in

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

Avoid the next call-out bill

Monthly cover means no unexpected bills when your boiler breaks down.

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

S.01View →S.02View →S.03View →

All 153 fault codes on the ecoTEC sustain

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

conConnectiond.00d.01d.02d.04d.05d.06d.07d.08d.09d.10d.11d.13d.14d.15d.16d.17d.18d.20d.21d.22d.23d.25d.27d.28d.33d.34d.35d.36d.39d.40d.41d.43d.45d.47d.50d.51d.58d.60d.61d.64d.65d.66d.67d.68d.69d.71d.73d.75d.77d.80d.81d.82d.83d.84d.85d.88d.90d.91d.93d.94d.95d.96ErrF.00F.01F.1F.10F.11F.13F.20F.22F.23F.24F.27F.28F.29F.32F.46F.49F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.77F.83F.84F.85F.87F.88F.89F.97F22F70P.00P.01P.02P.06S.01S.02S.2S.03S.3S.04S.4S.05S.06S.6S.07S.08S.8S.10S.11S.13S.14S.15S.16S.17S.20S.21S.22S.23S.24S.25S.26S.27S.28S.30S.31S.32S.34S.39S.42S.53S.54S.88S.91S.96S.97S.98S.108S.109

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on a combi.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →