What to check, in order
- Don't try to fix it yourself
Worcester's manual says not to try to put E2 right yourself.
- Call a Gas Safe registered engineer
Tell them the code on the display.
When to call a Gas Safe engineer
Worcester's service booklet points to a corroded connector or a faulty sensor or sensor lead. The engineer replaces the sensor or its lead.
A repair visit will usually check the sensor's reading and its wiring.
Before you book
- Note the model and serial number. They're on a label on the data badge, usually under the boiler or behind the front cover.
- Write down the exact code, and what the appliance was doing when it appeared.
- Check whether it's still under warranty. If it is, the repair may cost you nothing.
Checked against
- Worcester Bosch Greenstar CDi Classic user instructions (PDF)
- Worcester Bosch Greenstar CDi Classic engineer's service booklet (PDF)
Last reviewed September 2026. Manufacturers update their pages, and your manual is the final word.