Bosch Boiler Error Codes — Meanings, Causes & Repair in Greater Vancouver

Seeing a fault code on your Bosch boiler? This guide explains what the most common Bosch boiler error codes mean, what’s safe to check yourself, and when to call HeatLand’s licensed, TSBC-certified gas technicians for Bosch boiler repair across Metro Vancouver and the Fraser Valley.

The codes below apply across common Bosch models (Bosch Greenstar (Greenstar i / Si / CDi / 8000), Buderus Logamax plus GB142, Buderus GB125, Buderus GB162, Buderus SSB). Meanings follow Bosch’s documented fault codes — always confirm against your unit’s own manual, because exact wording can vary by model, control board and firmware.

How to read Bosch boiler error codes

Bosch Greenstar displays a 2-character alphanumeric fault code (e.g. EA, C1, A1, E9, FD) — newer Greenstar 8000 / GB162 models add a 3-4 digit numeric sub-code (e.g. EA 227, C1 264, 1017). Buderus Logamax (GB142/GB125) with the BC10 controller flashes a 2-character display code (e.g. 6A, 2P, 4C, 3C, 9L) that maps to a UBA3 numeric fault number (e.g. 6A=227, 2E=207). Both share the same Bosch EMS control platform, so many code meanings overlap. A solid display = blocking/info fault; a flashing code = lockout requiring reset.

Bosch boiler error codes & what they mean

These are the Bosch boiler codes our Greater Vancouver technicians see most. Anything marked pro repair involves gas, electrical, sealed-combustion or control-board work that must be done by a licensed gas technician (TSBC-certified in BC) — never open gas or electrical components yourself.

Code	What it usually means	Common causes	Safe to check yourself
EA / 6A (227)	No flame / no ionisation detected — burner attempted ignition several times and could not establish or confirm a stable flame, so the boiler locked out for safety pro repair	No gas supply or gas cock turned off; Frozen or blocked condensate drain (very common in winter); Low gas pressure	Confirm other gas appliances work / gas is on at the meter; Check the external condensate pipe is not frozen; if frozen, thaw the visible outdoor section with warm (not boiling) water; Perform a single reset and observe whether the fault returns
C1 (264)	Fan stopped or lost signal during operation — the fan is not running correctly while the boiler is firing, which prevents safe flue-gas removal pro repair	Failed or seized fan motor; Blocked or obstructed flue; Wiring / connector fault to the fan	Check the flue terminal outside is not blocked or obstructed; Confirm mains power is stable (no flickering/brownout); Perform a single reset
C7 / 3A (264)	Fan not running at start-up — the fan failed to start when the boiler tried to begin a heating or hot-water cycle pro repair	Failed fan; Fan wiring or connector fault; Blocked flue / air intake	Check the outside flue terminal for blockage or debris; Perform a single reset
C6 / 3C / 3P (216)	Fan speed fault — the fan cannot reach or is not maintaining the required (target) speed pro repair	Failing fan bearing/motor; Blockage in flue restricting fan; Wiring fault	Check the outdoor flue terminal for obstruction; Perform a single reset
A1 / 2L (266)	Pump fault — pump is stuck, running dry, or not generating the required flow/pressure difference (often air in the system or a leak) pro repair	Air trapped in the system; Low system pressure / water leak; Seized or failed circulation pump	Read the system pressure gauge — it should typically sit around 1.0–1.5 bar when cold; Look for visible water leaks around the boiler and pipes; Perform a single reset
A7	Domestic hot water (DHW) temperature sensor fault / defect pro repair	Faulty DHW NTC sensor; Damaged sensor wiring or connector	Perform a single reset and note whether hot water still functions
E9 / 4C (224)	Safety temperature limiter / overheat lockout — the high-limit thermostat tripped because the boiler sensed excessive temperature pro repair	Low system pressure; Trapped air in the system; Seized or failed circulation pump	Read the system pressure gauge (typically ~1.0–1.5 bar cold); Confirm radiator/system isolation valves are open (if visible and clearly marked); Perform a single reset
E2 / 4Y (223)	Central-heating flow temperature sensor fault — open circuit or defective flow (supply) NTC sensor pro repair	Faulty flow NTC sensor; Damaged sensor wiring / connector	Perform a single reset
E5 / 4A (218)	Flow temperature too high — supply sensor measured a temperature above the safe threshold (approx. 105 °C / 221 °F) pro repair	Poor circulation (air, low pressure, failing pump); Blocked heat exchanger; Faulty sensor	Check system pressure on the gauge; Perform a single reset
FA / 6C (228/306)	Flame / ionisation signal still detected after the gas valve has closed (false or persistent flame signal) pro repair	Faulty gas valve not closing fully; Faulty ionisation/flame electrode or wiring; Control board fault	Perform a single reset
F7	Flame (or flame signal) detected when the boiler should be off — unexpected ionisation current pro repair	Faulty flame-sensing electrode or wiring; Moisture/condensation on electrode or PCB; Gas valve not sealing	Perform a single reset
6C (228)	Ionisation current detected before the burner was activated (Buderus) / safety valve leak indication — flame signal present before ignition pro repair	Gas valve leaking / not sealing; Faulty ionisation electrode or wiring; Control board fault	Perform a single reset
6L (229)	Flame / ionisation lost during operation (Buderus) — flame failed while the burner was running pro repair	Marginal gas pressure; Dirty or failing flame electrode; Partial flue/condensate restriction	Confirm gas is on and other appliances work; Check condensate pipe is not frozen/blocked; Perform a single reset
F0 / E (242–290)	Internal control box / electronics (UBA / PCB) error pro repair	Internal PCB fault; Loose internal connector; Electrical interference	Perform a single reset
FD	Reset button pressed by mistake (or accidental reset). Informational — usually clears on its own DIY-checkable	The reset button was pressed when no fault was present	No action usually needed; if heating resumes normally, ignore; Perform a single reset if it persists
9U (233) / 9A / 9P / 9H	Code plug / KIM (key identification module) or UBA3 control fault — invalid or missing code plug, or defective control board pro repair	Missing, loose or faulty code plug / KIM; Defective UBA3 / control board; Connector not seated after a service	Perform a single reset
9L (234)	Gas valve coil or wiring defective (Buderus) pro repair	Faulty gas valve modulating coil; Damaged gas valve wiring/connector; Control board fault	Perform a single reset
2E (207) / 1017 / 2971	System water pressure too low DIY-checkable	Gradual pressure loss over time; Water leak in the system; Recently bled radiators	Read the pressure gauge — if below ~1.0 bar (cold), pressure is low; Check for visible leaks at the boiler and around radiator valves; Re-pressurising via the filling loop is owner-doable only if you know your boiler's procedure; otherwise call a technician
2P (212)	Temperature gradient limit — boiler temperature is rising too rapidly in heating mode (poor heat dissipation/circulation) pro repair	Air in the system; Low system pressure; Pump or bypass circuit fault	Read the system pressure gauge; Confirm system valves are open if visible and clearly labelled; Perform a single reset
2U (213)	Supply-to-return temperature differential exceeds the allowed limit (Buderus) — indicates poor circulation across the heat exchanger pro repair	Failing pump / low flow; Air in system; Blocked / sludged heat exchanger	Check system pressure on the gauge; Perform a single reset
3Y (215)	Blower / fan running at excessive (too high) speed (Buderus) pro repair	Fan speed-signal fault; Flue resistance abnormality; PCB fault	Check the flue terminal for obstruction; Perform a single reset
3L (214) / 3F (273)	Blower (fan) deactivated or switched off during the safety self-test (Buderus) pro repair	Fan fault; Wiring/connector fault; Control board fault	Perform a single reset
4L (220) / 4P (227)	Safety (high-limit) sensor fault — shorted/over-temperature (4L) or open circuit / interrupted contact (4P) on the safety NTC (Buderus) pro repair	Faulty safety temperature sensor; Damaged sensor wiring/connector; Genuine overheat condition	Check system pressure on the gauge; Perform a single reset
4U (222) / 4Y (223)	Supply (flow) sensor fault — short circuit (4U) or interrupted/open contact (4Y) on the flow NTC (Buderus) pro repair	Faulty flow NTC sensor; Damaged wiring/connector	Perform a single reset
CU (240) / CY (241) / CA (286)	Return temperature sensor fault — short circuit (CU), interrupted/open contact (CY), or over-temperature (CA, above ~105 °C / 221 °F) (Buderus) pro repair	Faulty return NTC sensor; Damaged wiring/connector; Poor circulation causing genuine over-temperature	Check system pressure on the gauge; Perform a single reset
CL	Domestic hot water temperature sensor fault (Buderus) pro repair	Faulty DHW NTC sensor; Damaged wiring/connector	Perform a single reset and note whether hot water still functions
B3	Short circuit / failure in the condensate water-level switch (Buderus) pro repair	Blocked condensate drain causing condensate backup; Faulty water-level/float switch; Wiring fault	Check the condensate drain pipe is not blocked or frozen (thaw outdoor section with warm water if frozen); Perform a single reset
D5	Condensate pump failure (Greenstar models fitted with an internal condensate pump) pro repair	Failed condensate pump; Blocked condensate outlet; Wiring fault	Check the condensate discharge pipe is not blocked or frozen; Perform a single reset
8Y (232)	External safety switch contact activated (e.g. an external limit/interlock device in the circuit has opened) (Buderus) pro repair	External low-water-cutoff or limit device tripped; Wiring fault in the external interlock loop	Perform a single reset; if it recurs, an external safety device needs investigation
d7	Modulator coil fault — regulator valve coil on the gas valve (Buderus) pro repair	Faulty gas valve modulating coil; Damaged wiring/connector	Perform a single reset

Bosch boiler codes we get called for most

EA / 6A (227) — No flame / no ionisation detected — burner attempted ignition several times and could not establish or confirm a stable flame, so the boiler locked out for safety

Typical causes include no gas supply or gas cock turned off; frozen or blocked condensate drain (very common in winter); low gas pressure. A few things are safe to check yourself (Confirm other gas appliances work / gas is on at the meter; Check the external condensate pipe is not frozen; if frozen, thaw the visible outdoor section with warm (not boiling) water), but the repair is a licensed, TSBC-certified gas technician job. HeatLand diagnoses and fixes EA / 6A (227) on Bosch boilers throughout Greater Vancouver.

6L (229) — Flame / ionisation lost during operation (Buderus) — flame failed while the burner was running

Typical causes include marginal gas pressure; dirty or failing flame electrode; partial flue/condensate restriction. A few things are safe to check yourself (Confirm gas is on and other appliances work; Check condensate pipe is not frozen/blocked), but the repair is a licensed, TSBC-certified gas technician job. HeatLand diagnoses and fixes 6L (229) on Bosch boilers throughout Greater Vancouver.

A1 / 2L (266) — Pump fault — pump is stuck, running dry, or not generating the required flow/pressure difference (often air in the system or a leak)

Typical causes include air trapped in the system; low system pressure / water leak; seized or failed circulation pump. A few things are safe to check yourself (Read the system pressure gauge — it should typically sit around 1.0–1.5 bar when cold; Look for visible water leaks around the boiler and pipes), but the repair is a licensed, TSBC-certified gas technician job. HeatLand diagnoses and fixes A1 / 2L (266) on Bosch boilers throughout Greater Vancouver.

E9 / 4C (224) — Safety temperature limiter / overheat lockout — the high-limit thermostat tripped because the boiler sensed excessive temperature

Typical causes include low system pressure; trapped air in the system; seized or failed circulation pump. A few things are safe to check yourself (Read the system pressure gauge (typically ~1.0–1.5 bar cold); Confirm radiator/system isolation valves are open (if visible and clearly marked)), but the repair is a licensed, TSBC-certified gas technician job. HeatLand diagnoses and fixes E9 / 4C (224) on Bosch boilers throughout Greater Vancouver.

Is it safe to keep running a Bosch boiler with a fault code?

Most Bosch fault codes put the boiler into a safe lockout for a reason. You can safely check the basics — gas supply on, power on, the thermostat calling for heat, system pressure in the normal range, and the condensate drain not frozen or blocked (a common cause in Vancouver cold snaps) — and restart it once. If the code returns, stop and book a technician. If you ever smell gas, leave the building and call your gas utility’s emergency line or 911 first. If a carbon-monoxide alarm sounds, get everyone out and call 911.

Bosch boiler repair across Greater Vancouver

HeatLand has kept Metro Vancouver homes comfortable since 1999. Our licensed, insured technicians diagnose and repair Bosch boilers — ignition faults, flame and sensor errors, low-pressure and pump problems, fan and flue faults, and control-board issues — including units we didn’t install. We’re brand-agnostic, carry common parts, and give you an honest repair-or-replace assessment with upfront pricing and a free estimate. If your boiler is beyond economical repair, we’ll show you right-sized, high-efficiency replacement options and the rebates available.

Need it sorted fast? We offer priority emergency boiler repair. Explore Boiler services, browse all boiler error codes by brand, or request a free estimate.

Bosch boiler service areas

We repair Bosch boilers across Greater Vancouver and the Fraser Valley, including:

Bosch boiler error code FAQs

Can I reset my Bosch boiler myself?

Yes — power-cycling the reset button once is generally safe after you’ve checked the basics (gas supply on, power on, the thermostat calling for heat, system pressure in the normal range, and the condensate drain not frozen or blocked (a common cause in Vancouver cold snaps)). If the boiler faults again right away, stop and note the code — repeatedly resetting a boiler that keeps locking out can mask a real problem. Call a licensed, TSBC-certified gas technician to diagnose it.

What does the Bosch EA / 6A (227) code mean?

On Bosch boilers, EA / 6A (227) commonly indicates no flame / no ionisation detected — burner attempted ignition several times and could not establish or confirm a stable flame, so the boiler locked out for safety. Confirm the exact meaning against your unit’s manual — codes can vary by model and series — and have the repair done by a licensed, TSBC-certified gas technician. HeatLand fixes this across Greater Vancouver.

Do you repair Bosch boilers you didn’t install?

Yes. HeatLand is brand-agnostic and services Bosch boilers throughout Metro Vancouver and the Fraser Valley, whether or not we installed the unit. We carry common parts and give you an honest repair-or-replace assessment.

Is a Bosch boiler fault code an emergency?

No heat in cold weather is worth treating urgently. If you ever smell gas, leave the building and call your gas utility’s emergency line or 911 first. If a carbon-monoxide alarm sounds, get everyone out and call 911. For priority boiler repair across Greater Vancouver, call (604) 330-3812.

How much does Bosch boiler repair cost in Vancouver?

It depends on the fault. Many Bosch codes point to sensors, ignition or pump parts — usually far cheaper than replacement. We give upfront pricing and a free estimate before any work.

More Boiler error-code guides

HeatLand repairs every major boiler brand across Greater Vancouver. More brand guides: