ATAG error codes
Find the meaning of ATAG fault, warning and status codes, with model context, documented causes, safe checks and links to available manufacturer guidance.
56documented codes
3products and models
1product categories
About ATAG error codes
An error code is a diagnostic clue, not a complete repair diagnosis. ATAG may reuse similar-looking codes across different products, model generations or regions, so always confirm the complete code and exact model before following instructions or ordering parts.
This profile connects every indexed ATAG code to its dedicated explanation page. Each page is structured around the search intent: a quick meaning, symptoms, likely causes, safe troubleshooting, reset guidance, applicable products and the point at which professional help is appropriate. Records marked as verified include the manufacturer or another authoritative technical source.
Start with the code shown on the display, then narrow the result by product or model. Do not assume that a reset has repaired the underlying fault. If a code returns, the product is unsafe, or diagnosis requires internal electrical, gas, refrigerant or moving components, stop and use an authorised technician.
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Popular ATAG codes
133ATAG · ATAG boilers · United KingdomIgnition failureATAG documents 133 for ATAG boilers as “Ignition failure”. This is the quick answer for this product context.…110ATAG · ATAG boilers · United KingdomSafety temperature exceededATAG documents 110 for ATAG boilers as “Safety temperature exceeded”. This is the quick answer for this product…105ATAG · ATAG boilers · United KingdomInsufficient circulationATAG documents 105 for ATAG boilers as “Insufficient circulation”. This is the quick answer for this product context.…78ATAG · ATAG boilers · United KingdomWater-pressure faultATAG documents 78 for ATAG boilers as “Water-pressure fault”. This is the quick answer for this product context.…61ATAG · ATAG boilers · United KingdomNo flame detectedATAG documents 61 for ATAG boilers as “No flame detected”. This is the quick answer for this product…50ATAG · ATAG boilers · United KingdomHot-water sensor faultATAG documents 50 for ATAG boilers as “Hot-water sensor fault”. This is the quick answer for this product…40ATAG · ATAG boilers · United KingdomReturn sensor faultATAG documents 40 for ATAG boilers as “Return sensor fault”. This is the quick answer for this product…20ATAG · ATAG boilers · United KingdomFlow sensor faultATAG documents 20 for ATAG boilers as “Flow sensor fault”. This is the quick answer for this product…
ATAG product groups
Code directory
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10ATAG · ATAG boilers · United KingdomOutside sensor faultATAG documents 10 for ATAG boilers as “Outside sensor fault”. This is the quick answer for this product…105ATAG · ATAG boilers · United KingdomInsufficient circulationATAG documents 105 for ATAG boilers as “Insufficient circulation”. This is the quick answer for this product context.…110ATAG · ATAG boilers · United KingdomSafety temperature exceededATAG documents 110 for ATAG boilers as “Safety temperature exceeded”. This is the quick answer for this product…133ATAG · ATAG boilers · United KingdomIgnition failureATAG documents 133 for ATAG boilers as “Ignition failure”. This is the quick answer for this product context.…20ATAG · ATAG boilers · United KingdomFlow sensor faultATAG documents 20 for ATAG boilers as “Flow sensor fault”. This is the quick answer for this product…40ATAG · ATAG boilers · United KingdomReturn sensor faultATAG documents 40 for ATAG boilers as “Return sensor fault”. This is the quick answer for this product…50ATAG · ATAG boilers · United KingdomHot-water sensor faultATAG documents 50 for ATAG boilers as “Hot-water sensor fault”. This is the quick answer for this product…61ATAG · ATAG boilers · United KingdomNo flame detectedATAG documents 61 for ATAG boilers as “No flame detected”. This is the quick answer for this product…78ATAG · ATAG boilers · United KingdomWater-pressure faultATAG documents 78 for ATAG boilers as “Water-pressure fault”. This is the quick answer for this product context.…10ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 10 error code – Outdoor sensor faultATAG identifies code 10 as: Outdoor sensor fault.105ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 105 error code – Venting programme activeATAG identifies code 105 as: Venting programme active.110ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 110 error code – Safety temperature exceededATAG identifies code 110 as: Safety temperature exceeded.111ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 111 error code – Maximum pressure exceededATAG identifies code 111 as: Maximum pressure exceeded.117ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 117 error code – Pressure above 3 bar or pump pressure rise too highATAG identifies code 117 as: Pressure above 3 bar or pump pressure rise too high.118ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 118 error code – Pressure below 1 bar or pump pressure rise too low; pump not detectedATAG identifies code 118 as: Pressure below 1 bar or pump pressure rise too low; pump not detected.119ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 119 error code – Link missing at X2 positions 4 and 5ATAG identifies code 119 as: Link missing at X2 positions 4 and 5.129ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 129 error code – Fan does not startATAG identifies code 129 as: Fan does not start.133ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 133 error code – No flame after five ignition attemptsATAG identifies code 133 as: No flame after five ignition attempts.151ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 151 error code – Fan speed control fault or defective control unitATAG identifies code 151 as: Fan speed control fault or defective control unit.154ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 154 error code – Flow temperature rising too quickly or return hotter than flowATAG identifies code 154 as: Flow temperature rising too quickly or return hotter than flow.20ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 20 error code – Flow sensor faultATAG identifies code 20 as: Flow sensor fault.40ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 40 error code – Return sensor faultATAG identifies code 40 as: Return sensor fault.50ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 50 error code – Domestic hot-water sensor faultATAG identifies code 50 as: Domestic hot-water sensor fault.61ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 61 error code – Bus communication faultATAG identifies code 61 as: Bus communication fault.78ATAG · ATAG iC, iS and iR boiler range — 2015 to 2018 · United KingdomATAG 78 error code – Water pressure out of rangeATAG identifies code 78 as: Water pressure out of range.101ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 101 error code – OverheatATAG identifies code 101 as: Overheat.102ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 102 error code – Pressure sensor errorATAG identifies code 102 as: Pressure sensor error.103ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 103 error code – Flow check failed three times; last failure check 1ATAG identifies code 103 as: Flow check failed three times; last failure check 1.104ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 104 error code – Flow check failedATAG identifies code 104 as: Flow check failed.105ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 105 error code – Flow check failed three times; last failure check 3ATAG identifies code 105 as: Flow check failed three times; last failure check 3.106ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 106 error code – Flow check failed three times; last failure check 4ATAG identifies code 106 as: Flow check failed three times; last failure check 4.107ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 107 error code – Flow check 5 failedATAG identifies code 107 as: Flow check 5 failed.108ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 108 error code – Water pressure below 0.5 bar; filling neededATAG identifies code 108 as: Water pressure below 0.5 bar; filling needed.109ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 109 error code – Water pressure above maximumATAG identifies code 109 as: Water pressure above maximum.110ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 110 error code – Flow temperature probe damagedATAG identifies code 110 as: Flow temperature probe damaged.112ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 112 error code – Return temperature probe damagedATAG identifies code 112 as: Return temperature probe damaged.114ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 114 error code – Outdoor temperature sensor damagedATAG identifies code 114 as: Outdoor temperature sensor damaged.118ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 118 error code – Flow and return probe plausibility check failedATAG identifies code 118 as: Flow and return probe plausibility check failed.140ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 140 error code – Dynamic pressure check failed or pump not detectedATAG identifies code 140 as: Dynamic pressure check failed or pump not detected.141ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 141 error code – Central-heating flow switch openATAG identifies code 141 as: Central-heating flow switch open.1P1ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 1P1 error code – Flow check 1 failedATAG identifies code 1P1 as: Flow check 1 failed.1P2ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 1P2 error code – Flow check 3 failedATAG identifies code 1P2 as: Flow check 3 failed.1P3ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 1P3 error code – Flow check 4 failedATAG identifies code 1P3 as: Flow check 4 failed.1P4ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 1P4 error code – Water pressure between 0.5 and 0.8 bar; filling neededATAG identifies code 1P4 as: Water pressure between 0.5 and 0.8 bar; filling needed.1P9ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 1P9 error code – Dynamic water-pressure checkATAG identifies code 1P9 as: Dynamic water-pressure check.201ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 201 error code – Domestic hot-water probe damagedATAG identifies code 201 as: Domestic hot-water probe damaged.203ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 203 error code – Cylinder probe damagedATAG identifies code 203 as: Cylinder probe damaged.303ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 303 error code – PCB faultATAG identifies code 303 as: PCB fault.304ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 304 error code – Too many resetsATAG identifies code 304 as: Too many resets.306ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 306 error code – PCB faultATAG identifies code 306 as: PCB fault.309ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 309 error code – Gas relay check failedATAG identifies code 309 as: Gas relay check failed.41ZATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 41Z error code – Room sensor zone unavailableATAG identifies code 41Z as: Room sensor zone unavailable.501ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 501 error code – No flame detectedATAG identifies code 501 as: No flame detected.502ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 502 error code – Flame detected with gas valve closedATAG identifies code 502 as: Flame detected with gas valve closed.504ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 504 error code – Flame lift detectedATAG identifies code 504 as: Flame lift detected.5P2ATAG · ATAG iC, iS and iR boiler range — 2019 and newer · United KingdomATAG 5P2 error code – First ignition attempt failedATAG identifies code 5P2 as: First ignition attempt failed.