Er.4 Emergency

Vaillant Er.4 Fault Code

Also written as ER4 — same fault.

The Vaillant Er.4 fault code means: your boiler is failing to ignite because it cannot receive the gas supply required to produce a flame.. It appears on 1 Vaillant model in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: Gas valve (LPG or Natural gas)
Typical repair cost £150-350 (including labour)

Engineer required

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

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Vaillant models that show the Er.4 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant Er.4 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026