Error E154

Safety first

- If you smell gas, leave the property immediately, call the gas emergency number and do not operate electrical switches or the boiler.

- Turn off the boiler and isolate the electrical supply before touching any parts. If you are not comfortable working near the appliance, stop and call a Gas Safe registered engineer.

- Do not open the boiler casing or touch wiring or components unless you are qualified to do so.

Initial checks a homeowner can do

1. Record the exact fault code and any other codes or lights shown on the display. Note whether heating, hot water or both are affected. This helps the engineer diagnose more quickly.

2. Try a simple reset. Use the boiler reset button or the selector to R and hold for about 5 to 10 seconds. Watch if the boiler attempts to restart and whether the E154 returns immediately or after a short period.

3. Check system water pressure on the pressure gauge. Aim for around 1 to 1.5 bar when cold for most domestic Baxi boilers. If pressure is below about 0.7 bar, top up using the filling loop according to the boiler handbook. After topping up, reset the boiler and check if the fault clears.

4. Bleed radiators to remove airlocks. Air in the system is a common cause of poor circulation. After bleeding, check and re-pressurise the system if pressure has dropped.

5. Ensure radiator and boiler isolation valves (flow and return shut-off valves) are fully open. Also check that the heating thermostat and programmer are calling for heat.

Specific diagnostic checks

1. Check for pump activity. When the heating is calling, carefully feel the pipes to and from the pump (do not touch wiring). The flow pipe should get hot and the return should be noticeably cooler. If both remain similar cold/hot or the pump is silent, the pump may be seized or electrically not running.

2. Listen for unusual noises from the pump or boiler during a call for heat. Loud grinding or continuous humming can indicate a failing pump or trapped air.

3. Inspect accessible filters and the magnetic dirt trap if you have one fitted. A heavily contaminated filter can restrict flow. Cleaning or removing the filter usually requires isolating and partially draining the system; consider a professional if you are unsure.

4. Look for obvious loose connectors on visible sensor leads at the outside of the boiler casing, but do not open the PCB area or perform electrical repairs. A loose flow/return sensor connector can sometimes be reseated, but if this requires removing covers that expose mains wiring, call an engineer.

5. If the boiler displays additional codes (for example E125, E118, E119 or others) note them and include them when you call an engineer, as they indicate related issues such as low pressure or circulation faults.

If the fault clears after these steps

- Monitor the system for recurrence over the next 24 to 48 hours. If E154 returns, do not keep repeatedly resetting the boiler; arrange for a Gas Safe engineer.

When to call a professional

- If the pump appears not to run, is noisy, or the flow/return temperatures are not as expected after your checks.

- If pressure will not hold or keeps dropping after topping up, or you are unable to repressurise safely.

- If you suspect a failed temperature sensor, wiring fault, blocked heat exchanger, or if cleaning filters requires draining the system.

- If the error persists after bleeding, repressurising and a reset, or if additional fault codes appear.

What to tell the engineer

- Boiler model and exact error code E154, other codes or lights, what you have already checked (pressure, bleeding, reset, pump behaviour), and whether there has been recent work or changes to the heating system.

Important warnings and final notes

- Do not attempt gas valve, burner, PCB, or internal wiring repairs yourself. These must be performed by a Gas Safe registered engineer.

- Do not repeatedly reset the boiler; excessive resets can cause further damage or mask a developing fault.

- If in doubt or if the fault returns, book a qualified engineer to inspect and repair the primary circulation, replace or recalibrate sensors, or carry out safe component replacements and system cleaning.