- Boilers
- Gas boiler
E2
Worcester E2 on a gas boiler: flow temperature sensor fault
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On Greenstar CDi boilers, E2 means the central heating flow temperature sensor (NTC) reads as defective, so the boiler cannot control heating temperature. Reset once for 3 seconds; if E2 returns, call a Gas Safe registered engineer.
Safety first
Stop and check this first
- Do not open the boiler casing to look for the sensor: Worcester restricts servicing to Gas Safe registered engineers.
- If you smell gas: do not smoke or strike matches, do not operate electrical switches or unplug anything, do not use the phone or ring doorbells. Turn off the gas at the meter, open windows and doors, warn your neighbours and leave. Well away from the building, call the National Gas Emergency Service on 0800 111 999.
Safe checks you can perform
- Code and display
- One reset
- Pressure gauge reading
- Sensor circuit measurement
Leave these tasks to a qualified professional
- Do not attempt this professional task: Connector inspection
- Do not attempt this professional task: Resistance measurement against the table
- Do not attempt this professional task: Safety checks after closing the boiler
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Connector inspection
What they doThe engineer checks the flow NTC connector for corrosion, damage or dirt and remakes it.
They must show youthe connector condition.
In writingwhat was found and cleaned or replaced.
Resistance measurement against the table
What they doWith the power off, the engineer measures sensor resistance at the PCB connector and at the sensor and compares it with the booklet's table for the measured temperature.
They must show youthe measured value and the table value.
In writingboth values and the reference of any part replaced.
Safety checks after closing the boiler
What they doAfter work inside the casing, the engineer checks the case seal and runs the boiler, checking combustion as the installation instructions require.
They must show youthe boiler running on heating without E2.
In writingthe checks done before leaving.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Code and display
- Who:
- you.
- How:
- note whether the display shows E2 steadily or only now and then, and whether anything leaked near the boiler.
- Result that matters:
- whether the fault is constant or intermittent.
- If it comes and goes or there was water nearby:
- a connector fault is more likely; tell the engineer.
- If it is constant:
- the sensor or lead is the first suspect.
- Evidence to keep:
- a photo of the display and a note of dates.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179 · Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
One reset
- Who:
- you.
- How:
- press the reset button for three seconds.
- Result that matters:
- whether E2 clears.
- If E2 returns at once:
- leave the boiler and call a Gas Safe registered engineer; Worcester says not to rectify listed faults yourself.
- If it clears:
- note it; repeats confirm an intermittent connection.
- Evidence to keep:
- a note of each reset.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179
Pressure gauge reading
- Who:
- you.
- How:
- read the gauge with the boiler cold; 1.5 bar is the optimum Worcester gives.
- Result that matters:
- whether the boiler also lacks water.
- If it is below 1 bar:
- top up as the user guide shows and mention it; it does not explain E2 by itself.
- If it is correct:
- the fault stays with the sensor circuit.
- Evidence to keep:
- a photo of the gauge.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179
Sensor circuit measurement
- Who:
- a Gas Safe registered engineer.
- How:
- inspects the connector, then measures sensor resistance at the 20-pin connector and at the sensor against the table.
- Result that matters:
- where the reading departs from the table.
- If the sensor itself is out:
- the NTC is replaced.
- If only the lead or connector is out:
- they are cleaned or replaced.
- Evidence to keep:
- the measured resistance and temperature written down.
The sensor is inside the boiler casing near mains wiring and the gas circuit; only a Gas Safe registered engineer opens it.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179 · Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Worcester Bosch
- Product type
- Gas boiler
Known code variants
- Bosch E2 caldera
- Candy 2 flashes
- Candy 2 parpadeos
- Candy dishwasher 2 flashes
- Candy dishwasher E2
- Candy dishwasher error E2
- Candy dishwasher not filling with water
- Candy lavadora E2
- Candy lavavajillas E2
- Candy washer E2
- Candy washer not filling
- Candy washing machine error E2
- Cerapur E2
- CHECK WATER
- COMPROBAR AGUA
- De'Longhi dehumidifier E2 E3 sensor
- De'Longhi E2
- De'Longhi E3
- DeLonghi DD230P E2
- deshumidificador De'Longhi E2 E3 sensor
- deshumidificador Meaco E2 sensor de humedad
- E02
- E-2
- E2 Worcester
- E3
- error E2 frigorífico Indesit
- Error E2 Junkers
- error E2 lavadora Candy
- error E2 lavadora Samsung
- error E2 lavavajillas Candy
- error E2 lavavajillas Haier
- frigorífico combi Indesit E2 sensor
- Greenstar E2
- Haier dishwasher E2
- Haier dishwasher error E2
- Haier dishwasher not filling
- Haier E2
- Haier lavavajillas E2
- Indesit E2 error fridge freezer
- Indesit E2 frigorífico
- Indesit fridge freezer E2
- Indesit fridge freezer E2 sensor fault
- Junkers E2
- lavadora Candy no coge agua
- lavadora Samsung E2 agua en el tambor
- lavadora Samsung no desagua E2
- lavavajillas Candy 2 parpadeos
- lavavajillas Candy no coge agua
- lavavajillas Haier no coge agua
- Meaco dehumidifier E2 humidity sensor
- Meaco E2
- MeacoDry Arete E2
- NO WATER
- Samsung E2 desagüe
- Samsung E2 drain error
- Samsung E2 water left in drum
- Samsung lavadora E2
- Samsung washer error E2
- Samsung washer not draining E2
- Samsung washing machine E2
- Worcester boiler E2 fault
- Worcester Bosch E2
- Worcester E2
What it means
Worcester's user table lists E2 as the CH flow NTC sensor defective. The NTC is a temperature sensor on the heating flow pipe whose resistance changes with temperature. The service booklet checks whether the sensor connector is corroded, damaged or dirty, then measures resistance through the 20-pin connector and at the sensor against the booklet's table, before changing the lead, the sensor or the PCB. The code alone does not tell a failed sensor from a bad connection.
Warnings and stop conditions
- Mediumsource verified
Do not open the boiler casing to look for the sensor: Worcester restricts servicing to Gas Safe registered engineers.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179
- Criticalsource verified
If you smell gas: do not smoke or strike matches, do not operate electrical switches or unplug anything, do not use the phone or ring doorbells. Turn off the gas at the meter, open windows and doors, warn your neighbours and leave. Well away from the building, call the National Gas Emergency Service on 0800 111 999.
Evidence: Worcester Greenstar CDi Classic combi user instructions 6 720 812 179
Symptoms and causes
Probable causes · in order
- Corroded or dirty connectorPossible
Fits if E2 comes and goes, especially after a leak or damp near the boiler; the booklet checks the connector first.
Evidence: Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
- Faulty flow NTC sensorPossible
Fits if the sensor resistance, measured unplugged, does not match the table at the boiler's temperature.
Evidence: Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
- Lead or PCBLess common
Fits if the sensor measures correctly but the reading through the 20-pin connector does not; the lead assembly or PCB is changed.
Evidence: Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
Virtual technician
Does E2 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Health and Safety Executive · official_doc
- 2
Worcester Greenstar CDi Classic combi user instructions 6 720 812 179
Worcester Bosch · 2014 · manual
- 3
Worcester Greenstar CDi Classic engineer's service booklet 6 720 830 033
Worcester Bosch · 2014 · manual
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