Bosch boiler faults: fault codes, causes and parts (page 3 of 3)

Codes 301 to 377 of the 377 fault codes for Bosch. Looking for a specific code? Use the search on the first page.

Bosch boiler fault codes 301 to 377 of 377

The code list is split over 3 pages. Looking for a specific code? Use the search on the first page: it searches all 377 codes in one go.

Code	Cause
V or B8L534	No gas supply pressure. Flue gas pressure limiter is activated. Air pressure switch is activated. Air pressure switch is defective.
V or B8L534	Insufficient gas supply pressure. Flue gas pressure limiter is activated. Air pressure switch is activated. Air pressure switch is defective.
V2U533	Boiler or pump hydraulically connected incorrectly
V2U575	Flow ISTB (intelligent safety temperature limiter)
V3C537	No speed
V3C538	Fan speed too low
V3C540	Fan speed too high
V4A520	Flow ISTB (intelligent safety temperature limiter)
V4A575	Activation of the ISTB (intelligent safety temperature limiter)
V4A700	Factory default state
V4U521	Sensor difference between temperature sensors 1 and 2 too large.
V4U521	Sensor difference between temperature sensors 1 and 2 too large.
V4U522	Temperature sensor short circuit between temperature sensors 1 and 2.
V4U524	Temperature sensor short circuit
V4Y523	Boiler temperature sensor open circuit
V6A578	No flame within the safety time
V6C576	Ionisation current during pre-purge >0.9μA.
V6C576	Ionisation current during pre-purge > 0.9 μA
V6L561	5 times "Power up" (power interruption during the burner start).
V6L561	5 times "Power up" (power interruption during the burner start)
V8P580	Solenoid valve 1 leaking
V8U581	Solenoid valve 2 leaking
V9Y500 501 502 503	Internal fault of burner control unit relay
V9Y500, 501, 502, 503	Internal fault of burner control unit relay
VA01800	Outdoor temperature sensor is defective
VA01808	DHW temperature sensor 1 defective. If necessary, deactivate the hot water function
VA01808	DHW temperature sensor 1 defective. If necessary, deactivate the hot water function.
VA01810	Hot water stays cold
VA01845	Hydraulic configuration is not supported
VAD1818	Heat generator stays cold
VCO568	Water pressure sensor fault (cable break)
VCO569	Water pressure sensor fault (short circuit)
VCY566	Return temperature < 5 °C (open circuit)
VCY566	Return temperature <5°C (open circuit)
VCY567	Return temperature >130°C (short circuit)
VCY567	Return temperature > 130 °C (short circuit)
VCY573	Flow temperature < 5 °C (open circuit)
VCY573	Flow temperature <5°C (open circuit)
VCY574	Flow temperature >130°C (short circuit)
VCY574	Flow temperature > 130 °C (short circuit)
VEE601	Temperature sensor measurement (dual sensor)
VEE612	Return temperature sensor measurement
VEE613	Flow temperature sensor measurement
VLL571	Too many restarts despite reset
VLP570	Too many resets via the interface
b1	Coding plug not recognised.
b1	Coding plug.
b2, b3	Internal data error.
b2/b3/ b4/b5/b6	Internal data error.
b2/b3/b4/b5/b6	Internal data error.
b7257	The burner control unit or the KIM is defective.
d1	Return temperature sensor defective.
d1	LSM in lockout.
d1	No feedback voltage from LSM.
d1240	The contacts of the return temperature sensor are short-circuited.
d1241	The contacts of the return temperature sensor are open-circuit.
d1242	The burner control unit or the KIM is defective.
d1243	The burner control unit or the KIM is defective.
d1244	The burner control unit or the KIM is defective.
d1245	The burner control unit or the KIM is defective.
d1247	The burner control unit or the KIM is defective.
d1248	The burner control unit or the KIM is defective.
d1249	The burner control unit or the KIM is defective.
d1255	The burner control unit or the KIM is defective.
d3	Temperature limiter TB1 defective. External limiter has tripped. Temperature limiter in lockout.
d3	Temperature limiter TB 1 defective. External temperature limiter has switched off. Temperature limiter in lockout.
d3	Jumper 8-9 not recognised.
d3	Temperature limiter TB 1 defective. External temperature limiter has switched off. Temperature limiter is in lockout.
d3232	The external switching contact is open.
d4213	The temperature measured by the flow temperature sensor or the return temperature sensor rises too quickly.
d4286	The return temperature sensor has measured a heating return temperature higher than 105 °C.
d4342	The temperature measured by the flow temperature sensor rises too quickly.
d5	External flow temperature sensor defective (open diverter). External flow temperature sensor was recognised as a bus device and then connected differently.
d5	External temperature limiter defective (low loss header). External flow sensor was recognised as a bus device, disconnected and connected at a different location.
d7	Gas valve defective or modulation cable not connected.
dP	Gradient limitation: temperature rise too rapid.
rE	A reset of the boiler is being carried out.

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