Johnson & Starley E16 Fault Code: Causes, Fixes & Repair Costs
What does the Johnson & Starley E16 fault code mean?
E16 on a Johnson & Starley unit is a sensor stuck lockout: a monitored temperature sensor's reading has stopped moving when it should be changing. During heat-up and cool-down the controller expects every temperature it watches to track the appliance's behaviour; a value that sits flat through a firing cycle is a failed sensor, not a stable temperature, and the unit locks out rather than control against it. E16, E17 and E18 form a family — the same stuck-sensor supervision applied to different sensor channels — so the on-site job is the same for each: identify which probe has frozen, confirm with a resistance check, and replace it.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Sensor element failed frozen Common
The affected thermistor's output has stopped tracking real temperature — the element has failed in place. Confirmed by comparing its resistance against the temperature table while the unit heats and cools.
- Wiring holding the reading constant Sometimes
A partial short or a damaged lead can pin the measured value so it no longer moves; the loom is checked before the sensor is condemned.
- Board measuring-input fault Rare
If a known-good sensor still reads flat at the board, the measuring input itself has failed and the PCB is replaced.
How to fix it
- Reset once and observe DIY safe
Use the reset control (or switch off at the fused spur for 30 seconds and back on) a single time. If the code returns, stop resetting and book a Gas Safe registered engineer.
- Have a Gas Safe registered engineer complete the documented checks Gas Safe engineer
The engineer will watch the affected sensor's live reading through a heat-up cycle — a healthy thermistor moves continuously; a stuck one sits flat. They will then measure its resistance against specification and replace the sensor, repair the wiring, or (rarely) replace the board.
Parts you may need
- Temperature sensor (NTC thermistor) · from £25
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £90–£250, depending on the underlying cause.
Frequently asked questions
What does E16 mean on my Johnson & Starley?
A temperature sensor's reading has frozen — it stopped changing when the unit's real temperature was moving, which means the sensor (or its wiring) has failed. The controller locks out rather than heat blind. An engineer identifies the stuck channel and replaces the probe; a quick, inexpensive repair.
How is E16 different from E17 and E18?
They are the same stuck-sensor check on different sensor channels — the code tells the engineer which circuit to start with. From a homeowner's point of view all three mean the same thing: a failed temperature probe needing replacement.
Can I just keep resetting it?
One reset is fine to rule out a glitch. Beyond that you are asking the unit to run without a working temperature reading, which it will rightly refuse — book the repair instead.