E.00-.05 Boiler Fault Code: What It Means on Every Brand

The E.00-.05 fault code appears on 2 boiler brands — Baxi and Remeha — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.

Lockout — engineer likely 2 brands use this code

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What E.00-.05 means	Severity	DIY?
BBaxi	The E.00-.05 fault code on Baxi boilers indicates that the return water temperature sensor (an NTC thermistor) has been detected as short-circuited by the boiler's PCB. Full guide →	Lockout — engineer likely	No
RRemehashown as E.00.05	The E.00.05 code indicates that your Remeha boiler has detected a short circuit in the return temperature sensor — the NTC thermistor that monitors how hot the central heating water is… Full guide →	Lockout — engineer likely	No

E.00-.05 brand by brand

Baxi E.00-.05

The E.00-.05 fault code on Baxi boilers indicates that the return water temperature sensor (an NTC thermistor) has been detected as short-circuited by the boiler's PCB. This is a locking fault, meaning the boiler shuts itself down completely and will not fire again until the underlying problem has been resolved and the appliance manually reset. The return thermistor sits on the pipework carrying cooled water back into the boiler from your radiators. It feeds a continuous stream of resistance-based temperature readings to the control board, allowing the boiler to regulate output and protect itself from running outside safe temperature limits. When the PCB sees a resistance value consistent with a short circuit — rather than the expected range for a functioning sensor — it concludes the data cannot be trusted and locks out for safety.

Causes, fixes & costs for Baxi E.00-.05 → · All Baxi codes

Remeha E.00.05

The E.00.05 code indicates that your Remeha boiler has detected a short circuit in the return temperature sensor — the NTC thermistor that monitors how hot the central heating water is when it arrives back at the boiler. Because the sensor is sending a shorted, unreliable signal, the boiler's control board can no longer make safe decisions about heat output, so the boiler locks out as a precaution. This code sits within the broader E.00.xx family: E.00.04 typically signals an open circuit (broken connection) on the same sensor, while E.00.05 points specifically to a short circuit. Both codes ultimately mean the return sensor circuit needs investigation, but E.00.05 implies the resistance across the sensor or its wiring has collapsed rather than gone open.

Causes, fixes & costs for Remeha E.00.05 → · All Remeha codes

Frequently asked questions

Is the E.00-.05 fault code the same on every boiler?

Broadly, yes — on Baxi and Remeha the E.00-.05 code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.

Can I fix a E.00-.05 fault myself?

Not usually. On every brand listed, E.00-.05 points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.

Who should I call about a E.00-.05 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.