The Baxi E.00.17 fault code means “DHW tank temperature sensor short-circuited.” DHW means domestic hot water. In plain English, the boiler control has detected an electrical reading from the hot-water tank temperature-sensor circuit that is consistent with a short circuit.
This is a focused sensor-circuit message, not a general low-pressure or ignition fault. It also does not prove that the sensor itself has failed. The cause can only be established safely by an appropriately qualified engineer after checking the appliance, the connected controls and the installation.
Which Baxi boilers show E.00.17?
Baxi’s current error-code information places E.00.17 in a model group covering the Baxi 200, 400, 600 and 800 Combi 2; Baxi Assure 500 Combi 2; Baxi 600 and 800 System 2; and Baxi Assure 500 System 2.
However, the wording specifically refers to a hot-water tank temperature sensor. That means its practical relevance depends on how your heating and hot-water system is configured. Not every boiler in a shared error-code table will be connected to a separate cylinder or tank sensor in every home. Check the exact model name on the boiler and tell the engineer whether you have a hot-water cylinder.
What does “short-circuited” mean here?
The boiler monitors electrical signals from connected temperature sensors. E.00.17 says the signal from the DHW tank temperature-sensor circuit is outside the expected condition in a way Baxi describes as short-circuited.
That wording identifies what the control has detected. It does not identify one replaceable part with certainty. A professional may need to assess the sensor, its connection, the associated cable route and the boiler’s control response. Those checks involve electrical components and may involve the boiler casing, so they are not suitable homeowner jobs.
E.00.17 is also different from Baxi E.00.16. E.00.16 describes the DHW tank temperature sensor as not connected, whereas E.00.17 describes a short-circuit condition. The two messages concern the same broad sensing function but are not interchangeable.
What symptoms might you notice?
The exact behaviour depends on the installation. You may see the code with no stored hot water, water that is not reaching its normal temperature, or a boiler that has stopped part of its operation to protect the system. Heating may still behave differently from hot water.
Do not assume that apparently normal hot water means the message can be ignored. A reliable cylinder-temperature signal helps the controls manage stored hot water correctly.
Safe checks you can make
- Write down the full code exactly as shown, including the dots.
- Confirm the boiler’s complete model name.
- Note whether the home has a separate hot-water cylinder or tank.
- Check whether heating, hot water, or both have been affected.
- Record any other code shown before or after E.00.17.
- Tell the engineer about recent servicing, cylinder work, control changes or a power interruption.
Use only the user controls described in the guide for your exact boiler. Do not remove the casing or try to inspect, disconnect, test or replace the sensor, wiring, terminals, cylinder controls or circuit board. Do not use a meter to take resistance, voltage or continuity readings.
Should I reset the boiler?
If the user guide for your exact model permits a reset for this situation, one reset is reasonable. Baxi reset methods vary by model, so follow the correct guide rather than a generic sequence.
If E.00.17 returns, stop resetting it. Repeated resets do not correct a persistent circuit fault and may hide useful information about when the problem occurs. Keep the exact code available when arranging repair.
When should you stop using hot water?
If stored water is unexpectedly or dangerously hot, stop using it and arrange urgent professional help. Take particular care around children, older people and anyone with reduced sensitivity to heat.
If you smell gas, suspect fumes, or a carbon-monoxide alarm sounds, leave the property, avoid switches and flames, and follow the Gas Safe Register’s emergency guidance. Call the National Gas Emergency Service on 0800 111 999 from a safe place.
What will an engineer need to know?
Give the engineer the code, boiler model, whether a cylinder is fitted, and a short description of what the heating and hot water are doing. Mention whether the code followed recent work or a loss of power. This helps them arrive prepared while leaving all internal checks to a qualified professional.
For other safe fault-code explanations, visit the boiler help hub.
Need help with a recurring Baxi E.00.17 code?
Book a fixed-price boiler repair aimed at fixing the fault, with the booking price clear before the visit.
Quick answers about Baxi E.00.17
What does Baxi E.00.17 mean?
It means the DHW tank temperature-sensor circuit has been detected as short-circuited.
Does E.00.17 prove the tank sensor is broken?
No. The code describes a circuit condition. A qualified engineer must establish the cause.
Is E.00.17 the same as E.00.16?
No. E.00.16 means the tank sensor is not connected; E.00.17 means the circuit has been detected as short-circuited.
Can I keep resetting the boiler?
No. Use one reset only if the exact model guide allows it. If the code returns, arrange repair.
Can I test the sensor myself?
No. Do not open the boiler or test the sensor circuit, wiring or controls. These checks are for an appropriately qualified engineer.