E2 on a Worcester Bosch means the flow temperature sensor, the NTC on the heating flow, is defective or reading incorrectly.

This is a component fault rather than a system fault, and it is usually one of the more straightforward repairs on the list.

What E2 actually means

The boiler relies on that sensor to know how hot the water leaving it is. Every decision it makes about firing, modulating and shutting down depends on that reading.

If the reading is out of range, implausible, or the circuit is open, the boiler cannot trust it and stops.

What you can safely check yourself

Nothing useful. The sensor sits on the flow pipe inside the appliance.

It is worth noting whether the fault appears from cold, or only once the boiler has been running for a while, because that is genuinely useful information for whoever attends.

When to stop, and why

What causes it beyond the simple checks

A corroded, dirty or damaged sensor connector, a failed sensor, damaged wiring between the sensor and the PCB, or a PCB fault. The service booklet has the engineer check the connector for corrosion and damage before testing the sensor itself, because a poor connection is common and a lot cheaper to fix than a board.

How Vantage can help

We are Gas Safe registered under 956889 and cover Hertfordshire, Bedfordshire and Cambridgeshire, with an emergency line answered 24 hours a day. Call us on 01462 506374. See also boiler repair and boiler servicing.

Frequently asked questions

Is E2 serious?

It is not a safety fault in the way an overheat or a flame detection fault is. But the boiler will not run until it is sorted.

Will I definitely need a new sensor?

Not necessarily. A corroded connector or damaged wiring will give the same code. That gets checked first.

Can I keep resetting it?

You can try one reset. If it returns, it needs testing rather than clearing.

Related fault codes

Other Worcester Bosch codes: E9 · A1 · C6 · F0 · all Worcester Bosch codes. See also boiler repair and no hot water but heating works.

In Worcester Bosch’s own words

Worcester Bosch use different code sets across their ranges and generations. The definition above is taken from the Greenstar CDi Classic service booklet. If your boiler is a different model and the code behaves differently, check the manual for your appliance or ring us and we will tell you what it means on your unit.

When to call an engineer

If the checks above have not cleared it, the next steps are engineer work and the boiler should not be reset repeatedly in the meantime. Call Vantage Plumbing and Heating on 01462 506374. We are Gas Safe registered under 956889, the line is answered by a person at any hour of any day, and you get a price before anyone starts.

Need help today?

Call and speak to a person, any hour, any day of the year. Get a fixed price quote or call 01462 506374.