If your Baxi 600 System 2 shows E.00.16, Baxi’s current error-code table defines it as “DHW tank temperature sensor not connected.” On a system-boiler installation, “DHW tank” means the separate cylinder that stores hot water for taps and showers.
The boiler has not received the expected cylinder-temperature sensor signal. The wording does not prove that the sensor itself has failed or that somebody has physically unplugged it. A cable, connection, control arrangement or another part of the signal path may need professional checking.
What does Baxi E.00.16 mean?
The cylinder temperature sensor tells the heating controls how warm the stored water is. That information helps the system decide when the cylinder needs more heat and when reheating can stop. E.00.16 means the expected sensor connection is not being detected.
This is different from a combi boiler sensing hot water as it flows directly to a tap. The Baxi 600 System 2 works with a separate hot-water cylinder, so the fault may affect stored hot water even when the space-heating side appears to behave differently.
Does “not connected” mean the sensor is visibly unplugged?
No. It describes the missing signal detected by the boiler. The sensor may not be the failed part, and the problem may not be visible from outside. It would be unsafe to remove a boiler or cylinder cover, pull cables or open terminals to look for a loose connection.
An engineer needs to consider the complete installation, including how the cylinder controls are connected. The display alone cannot distinguish among a sensor, cable, connector, control or configuration issue.
What might you notice at home?
The stored hot water may fail to reheat, may not reach the usual temperature or may behave unpredictably. Space heating could still appear normal because the boiler can receive a separate demand from the heating controls. The exact effect depends on the installation and how its controls respond to the missing signal.
Do not use the temperature of one tap as proof that the fault has cleared. A cylinder can contain water at different temperatures, and previously heated water may remain available for a time even if reheating has stopped.
Safe observations to record
- Whether the radiators are heating normally.
- Whether the cylinder has reheated since E.00.16 appeared.
- Whether hot water starts warm and then quickly turns cool.
- Whether the fault appears only during a scheduled hot-water period.
- Whether any cylinder control or programmer shows an ordinary demand.
- Whether other codes appear before or after E.00.16.
- Whether recent work was carried out on the boiler, cylinder or controls.
Record only what can be seen or felt during normal use. Do not remove covers, trace cables behind panels or touch pipework that may be hot.
Can you reset E.00.16?
If the Baxi 600 System 2 display or its user guide specifically requests a reset, use the normal user reset once. Do not repeatedly reset the appliance if the code returns.
A reset allows the controls to check for the expected signal again. It cannot reconnect a circuit or repair a sensor. If E.00.16 remains or returns, professional repair is the appropriate next step.
What should you not try?
Do not remove the boiler casing or a cylinder thermostat cover. Do not disconnect, reconnect or bridge terminals. Never test resistance, continuity or voltage, and do not change installer settings in an attempt to make the code disappear.
A hot-water cylinder can contain very hot water, while the boiler contains gas and electrical components. Internal checks belong to a suitably qualified Gas Safe registered engineer who is competent to work on the connected cylinder controls.
Could the water become too hot?
The code says the expected temperature signal is missing; it does not tell you the actual cylinder temperature. Treat any unusually hot water seriously. Keep children and vulnerable people away from affected outlets, avoid testing with bare hands and arrange prompt help if water seems much hotter than normal.
If there is no hot water, do not increase unrelated boiler or programmer settings repeatedly. That will not restore a missing temperature signal and can make the system’s behaviour harder to understand.
When should you book a repair?
Book a repair when E.00.16 appears, particularly if the cylinder is not reheating or the hot-water temperature has become unreliable. A code that briefly clears and returns still needs attention because the expected sensor connection is not consistently available.
When booking, give the full Baxi 600 System 2 model name, the exact E.00.16 code and a short description of both heating and stored-hot-water behaviour. Mention recent work on the system, but do not attempt to inspect the connection yourself.
What information helps the engineer?
Keep the boiler display photograph, note the programmer setting and record the approximate time the cylinder last produced normally hot water. If the fault appeared after planned work, identify which part of the heating system was worked on without guessing what changed. This simple timeline is more useful than opening covers or trying to identify a particular sensor cable.
Gas and carbon-monoxide safety
E.00.16 is a temperature-sensor connection code and does not itself indicate a gas leak or carbon-monoxide event. General gas-safety rules still apply. If you smell gas, suspect a leak or a carbon-monoxide alarm sounds, stop using the boiler, move everyone into fresh air and call the National Gas Emergency Service on 0800 111 999 in Great Britain. Avoid electrical switches where gas may be present.
Possible carbon-monoxide symptoms include headache, dizziness, nausea, breathlessness, collapse or loss of consciousness. Seek urgent medical help if anyone may have been exposed.
Need the boiler repaired?
Your boiler fault is fixed for the agreed price, subject to eligibility and terms.
Quick answers
Does E.00.16 mean the cylinder sensor has failed?
No. It means the expected sensor signal is not connected from the boiler’s point of view. The sensor is only one part of the signal path.
Can heating still work?
It may. Space heating and cylinder reheating are separate demands, so record what each part of the system is doing.
Can I reconnect the sensor myself?
No. Do not open covers or touch wiring and terminals. Arrange qualified professional repair.
Is E.00.16 listed for the Baxi 600 System 2?
Yes. Baxi lists the code for the current Combi & System 2 group, which includes the Baxi 600 System 2.