All Boiler Fault Codes

Every boiler fault code in our database — 4,775 codes across all UK manufacturers. Click any code to see which brands and models display it, with plain English explanations and fixes.

Most common fault codes

These appear on the largest number of boiler models across the UK market.

0-9 (1498 codes)

-. / A -. / Y -9OC -ll- .0 (B) LED turning on (D) LED turning on (G) LED turning on ❍❍❍❍ (DHW) 00 - FF 0 (Flashing) 0 / A 0 / H 0 / Y 0 1. 0 2. 0 4 0 8 0 bar 0 nn 0 or -. / H 0 then 8 0-A1 0-A2 00:1 00:2 00:3 00:4 00:5 00:6 00. 0.0 0.5bar 0.8bar 0A 0A1 0A2 0A3 0A5 0A7 0A8 0A9 0A15 0A16 0A17 0A18 0A21 0A30 0A31 0A37 0A37 – Pro Tec 50 0A43 0A44 0A80 0b 0C 0D 0E 0E2 0E8 0E13 0E25 0E32 0E33 0E34 0E37 0E45 0E46 0E81 0E98 0E99 0F 0H 00h - FFh 0L 0U 0Y 01 0001 001 1 - IGNITION FAILURE 1 0 1 1 0 3 1 0 4 1 0 5 1 0 6 1 0 7 1 0 8 1 01 1 1 0 1 1 6 1 1 8 1 02 1 2 1 2 OUTDOOR SENSOR ERROR 1 03 1 04 1 05 1 06 1 07 1 8 1 08 1 09 1 9 1 10 1 12 1 14 1 16 1 18 1 flash green 1 flash red 1 green 1 green flash 1 nn 1 P 1 1 P 2 1 P 3 1 P1 1 P2 1 P3 1 P4 1 PILOT WILL NOT LIGHT 1 red flash 1 second ON 1 second OFF 1 then 2 1 to 9 1 to 9, h, l, b 1 to 24 01 to 99 1-2-3 1-A1 1-A2 1-A3 1-A5 1-A6 1-A7 1-b2 1-b3 1-b4 1-b7 1-b8 1-C1 1-C2 1-C4 1-C6 1-d1 1-d2 1-d3 1-d4 1-d5 1-E1 1-E2 1-E3 1-E4 1-EA 1-Eb 1. 1.A 1.b 1.C 1.d 1.E 1.W1 1.W2 1.W3 1.W4 1A 1A, 1B 1B 1C 1E:0 1E:1 1F 1J-64 1p1 1p2 1p3 1p4 1x 02 2 - CIRCULATION FAILURE 2 / P 2 / U 2 0 5 2 01 2 02 2 03 2 04 2 05 2 07 2 08 2 8 2 9 2 flashes 2 flashes green 2 flashes red 2 lights flashing fast 2 nn 2 pulses 2 pulses (No light) 2 red flashes 2 yellow 2. 2.0 2.2 2.4 2.5 2.6 2.7A 2.7bar 2.b 2.C 2.F 2a 2b 2C 02E 2E:0 2F 2F:0 2F:1 2F:2 2P 2S01 2S02 2U 2x 03 003 3 - OVERHEATING 3 + 3 0 1 3 0 2 3 0 3 3 0 4 3 0 5 3 0 6 3 0 7 3 0. 3 01 3 02 3 2. 3 03 3 04 3 05 3 06 3 6. 3 07 3 7. 3 bar or greater 3 CH yellow 3 flashes 3 flashes green 3 flashes red 3 green flashes 3 nn 3 P 9 3 P9 3 PILOT LIT, BUT NO MAINS GAS 3 red flashes 3.1 3.3 3.9 3.b 3.C 3.E 3.F 03E 3P9 3x 04 004 4 (Flashing Light) 4 (Flashing) 4 (Permanent Light) 4 (Permanent) 4 / A 4 / C 4 / L 4 / P 4 / U 4 / Y 4 + 4 1 1 4 1 2 4 1 3 4 07 4 flashes 4 flashes green 4 flashes red 4 green 4 green flashes 4 nn 4 red flashes 4-A1 4-A2 4-A4 4-A5 4-A6 4-b1 4-b2 4-b3 4-b4 4-b5 4-b6 4-E2 4-F1 4-F2 04, 05, 06, 08 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.F 04/05/06 04/06/07 4A 4C 04E 004E 4F 4L 4P 4U 4x 4Y 05 005 5 (Flashing Light) 5 (Flashing) 5 (Permanent Light) 5 (Permanent) 5 / Y 5 + 5 0 1 5 0 2 5 01 5 02 5 04 5 flashes 5 flashes green 5 flashes red 5 green flashes 5 nn 5 P 1 5 P 2 5 P 3 5 P1 5 P2 5 P3 5 P4 5 pulses 5 pulses (No light) 5 red 5 red flashes 5-A1 5-A2 5-A3 5.0 5.2 5.2.15 Error 517 5.2.19 Error 782 5.A 5.b 5.i 5.ii 5.iii 5.iv 5.v 5.vi 5.vii 5.viii 05/07/08 5A 5B:0 5B:1 05E 5P1 5P2 5P3 5S 5x 5Y 06 006 6 / C 6 / H 6 / L 6 + 6 1 0 6 1 2 6 1. 6 04 6 07 6 08 6 10 6 12 6 flashes 6 flashes green 6 flashes red 6 green flashes 6 nn 6 P1 6 P2 6 red flashes 6 yellow 6-7 6-t1 6-t2 6-t3 6-t5 6-tA 6-tb 6.4.1 Flame control 6.4.2 Thermostats 6.4.3 Water level control 6.4.7 Down draft thermostat 6.8 6.A 6.d 6.E 6.i 6.ii 6.iii 6.iv 6.v 06/07/08 6a 6b 6C 6C:0 to 6C:100 6C:100 6d 06E 6F:0 to 6F:100 6F:100 6H 6L 6P1 6P2 6x 07 007 7 - SAFETY SHUTDOWN 7 / A 7 01 7 02 7 03 7 04 7 05 7 06 7 07 7 11 7 12 7 13 7 22 7 23 7 50 7 flashes 7 green 7 nn 07, 09 7. 7.i 7.ii 7.iii 7.iv 7A 7b:0 7b:1 7C 7E:0 7E:1 7F 7F:0 7F:1 7H 7L 7x 08 008 8 (Diagnostic) 8 (Flashing) 8 flashes 8 nn 8 yellow 8-9 8. 8.1 8.2 8.2 Diagnostic LED Indicators 8.3 8.3 Faulting Finding Codes 8.4 8.4.1 8.4.2 8.5 8.6 8.7 8.8 8.10 8.11 8.12 8.13 8.14 8.15 8.A 8.b 8.C 8.d 8.E 8.F 8.i 8.ii 8.iii 8.iv 8A-46 8C 08E 8E 8H-65 8L 8x 09 9 (Flashing) 9 (w/ flashing b) 9 25 blinking 9 E 25 9 E 30 9 flashes 9 nn 9.1.2 9.1.3 9.1.4 9.1.5 9.1.6 9.1.7 9.1.8 9.1.9 9.1.10 9.1.11 9.1.12 9.1.13 9.1.28 9.1.29 9.1.30 9.1.31 9.1.34 9.1.35 9.1.36 9.1.37 9.3 9.A 9.b 9.C 9.d 9.E 9.F 9.i 9.ii 9.iii 9A 9A 361 9A 362 9A361 9A362 9B 9b:1 to 9b:127 9b:70 9C 9C:0 9C:5 to 9C:60 9C:20 09E 9F 9F:0 to 9F:40 9F:8 9F855 9F856 9H 9L 9P 9U 9U 233 9U233 9x 10 010 10-11 10-64 10-65 10.1 10.2 10.3 10.4 10.i 10.ii 10.iii 10.iv 10E 0011 011 11 + 11-64 11-65 11-66 11-67 12 012 12-13 12-64 12-65 12-66 12-67 12-68 12-69 13 013 13-64 / 13-65 13/14 13E 14 014 14-15 15 015 16 016 16 Per Sec 16-17 16-64 17 017 18 018 18-19 19 019 20 20-21 20/21/22 21 21:0 21:1 to 21:100 21E 22 + 22E 23 23:0 23:1 to 23:24 23/31 23E 24 024 24 V fuse blown 24:0 24:1 24E 25 025 25:0 25:1 25E 26 026 27 28 028 28:0 29 029 29E 30 030 30 (ll) 30 40 30 40 50 30 40 50 60 30 40 50 60 70 30 40 50 60 70 80 30 40 50 60 80 30 40 50 70 30 40 50 70 80 30 40 60 30 40 60 70 30 40 60 70 80 30 40 60 80 30 50 70 30 50 80 30 60 70 30 60 80 30 70 30 Flashing 30-80 (L, L, L, M, M, M) 30-80 (L, L, M, L, M, M) 30-80 (L, L, M, M, M, M) 30-80 (L, M, L, L, L, M) 30-80 (L, M, L, M, L, M) 30-80 (L, M, L, M, M, M) 30-80 (L, M, M, L, L, M) 30-80 (L, M, M, L, M, M) 30-80 (L, M, M, M, M, M) 30-80 (M, L, L, M, L, M) 30-80 (M, L, L, M, M, M) 30-80 (M, L, M, L, L, M) 30-80 (M, L, M, L, M, M) 30-80 (M, L, M, M, M, M) 30-80 (M, M, L, L, M, M) 30-80 (M, M, L, M, M, M) 30-80 (M, M, M, L, M, M) 30:0 30° neon flashing 30°C neon flashing 30c 31 031 31E 32 032 32:0 32/34 33/35 34 34:0 34:1 34:2 35 36 036 37 037 38 38:0 39 40 40 - 50 - 60 - 70 - 80 40 ●, 50 ●, red ● 40 ❍, 50 ❍, 60 ❍, yellow ❍ 40 ❍, 50 ❍, yellow ❍ 40 ❍, yellow ❍ 40 50 60 80 40 50 70 40 50 80 40 60 70 40 60 80 40 Flashing 40-50 (ll-ll) 40-50-70 (ll-ll-ll) 40-50-70-80 (ll-ll-ll-ll) 40-50-80 (ll-ll-ll) 40-60 (ll-ll) 40-60-70 (ll-ll-ll) 40-60-70-80 (ll-ll-ll-ll) 40-60-80 (ll-ll-ll) 40-70 (ll-ll) 40-80 (ll-ll) 40/06/08 40° neon flashing 40°C neon flashing 41 041 41E 42 042 42E 43 44 + 44E 45 45 -- 45 46 046 46E 47 047 48 49 50 50 - 60 - 70 - 80 50 (ll) 50 ●, 60 ●, red ● 50 ❍, 60 ❍, yellow ❍ 50 ❍, red ❍ 50 ❍, yellow ❍ 50 60 50 70 50 70 80 50 80 50 Flashing 50-59 50-60 (ll-ll) 50-60-70 (ll-ll-ll) 50-60-80 (ll-ll-ll) 50-70 (ll-ll) 50-70-80 (ll-ll-ll) 50-80 (ll-ll) 50:0 50:1 50:3 50/51/52 50° neon flashing 50°C neon flashing 51 52 52:0 52:1 53 53:0 53:1 53:2 53:3 53/54/55/56 54 54:0 54:1 54:2 55 -- 55 56 56:0 56:1 57 58 58:0 58:1 to 58:95 59 59:0 59:1 to 59:10 60 060 60 ●, 70 ●, 80 ●, red ● 60 ●, 70 ●, red ● 60 ❍, red ● 60 70 60 70 80 60 80 60 Flashing 60-70 (ll-ll) 60-70-80 (ll-ll-ll) 60-80 (ll-ll) 60:5 to 60:25 60:10 60:20 60/61 60° neon flashing 60°C neon flashing 61 62 62:0 62:1 to 62:15 62:2 63:0 63:1 63:2 to 63:14 63:15 65 65 L....8..... 65:0 65:1 65:2 65:3 66 H.....1..... 66C 67 H......F........ 67:0 to 67:60 67:40 68 68 H......4....... 69 69 H......n........ 70 70 ●, 80 ●, red ● 70 ❍, 80 ❍, yellow ❍ 70 ❍, red ● 70 ❍, yellow ❍ 70 80 70 Flashing 70-80 (ll-ll) 70/72/74 70° neon flashing 70°C neon flashing 71 71:0 71:1 71:2 71/73 72 72:0 72:1 72:2 73 73:0 73:1 to 73:6 73:7 74 75 75 / 76 75°C 76 76:0 76:1 76:2 77 + 77:1 77:2 to 77:99 78 78˚C 79 79:0 79:1 80 80 (ll) 80 ●, red ● 80 ❍, yellow ❍ 80 Flashing 80-01 80-83 80:0 80:1 80:2 to 80:199 80/90/91 80° neon flashing 80°C neon flashing 81 81-01 81-65 81:0 81:1 81:2 81:3 82 83 84 84 L....8..... 85 85 H.....1..... 85 H.....2..... 86 86 H.....2..... 86 H.....3..... 87 87 H.....3..... 87 H.....4.... 88 H......4....... 88 H......F..... 88:0 88:1 88° C 89 89 H......F........ 89 H......n..... 90 90 ●, red ● 90 ❍, yellow ❍ 90 Flashing 90 H......n........ 90:0 to 90:199 90:128 90˚C 91 91:0 91:1 91:2 91:3 92 93 93 H.....4.... 93/95 94 94 H......F..... 95 95 H......n..... 95:0 95:1 96 97 97:0 97:1 97:2 98 98:1 98:1 to 98:5 100 100° C 101 102 103 104 104H 105 105H 106 107 108 109 110 110˚C 110E 112 113 114 115 116 117 118 119 121 125 127 128 129 130 133 134 135 144 151 153 154 160 162 164 164-026 166 169-033 169-083 169-127 169-141 180 181 193 200 200 O 201 201 O 202 202 O 203 203 0 204 204 O 205 207 207 / CE 208 208 0 210 / E9 211 212 213 213 / D4 214 214 / C7 215 215 / C6 216 / C6 217 / C7 218 218 / E5 219 219 / E9 220 220 / E9 221 221 / E9 222 / E2 222-F 223 223 / E2 224 224 / E9 224 V 225 226 227 227 / EA 227 V 228 228 / F7 228 V 229 229 / EA 230 / EA 231 / FD 232 232 / D3 233 233 / 9U 234 234 / EA 235 237 237 / C4 238 238 / F0 239 / F0 240 240 / D1 241 241 / D1 242 242 F0 242 to 256 / F0 244 245 246 247 248 249 250 251 252 253 254 256 256 324 257 257 / b7 258 258 & 259 / F0 258 F0 259 259 327 260 261 261 EA 262 262 & 263 F0 263 264 264 C1 265 266 CE 267 F0 268 269 269 EA 270 271 D4 272 F0 273 273 C4 274 275 276 276 E9 277 277 E9 278 278 F0 279 F0 280 280 F0 281 281 A1 282 282 H5 283 284 285 285 E9 286 D1 287 F0 288 CF 289 CF 290 F0 300 301 302 303 304 305 305 0 306 306 FA 306 V 307 308 308 557 309 310 311 312 313 314 315 316 E9 317 A3 318 E9 319 494 321 322 323 323 A8 324 325 326 327 328 329 CE 332 332 E5 338 338 F0 341 341 D4 342 342 D4 343 ED 344 ED 345 EF 346 EC 347 347 E3 348 EE 349 EF 350 350 E2 351 351 E2 352 353 354 356 357 358 359 360 360 V 362 363 364 364 FA 365 365 Fb 372 373 8C 374 8C 375 E4 376 E4 380 381 656 383 598 384 386 575 398 051 398 055 400 401 403 404 405 406 407 408 410 411 412 413 414 415 416 417 421 424 426 430 431 432 433 436 437 441 442 460 501 502 504 515 517 522 528 529 547 568 578 591 594 601 604 610 612 615 660 661 662 668 669 701 702 703 704 705 706 707 711 712 713 722 723 727 728 729 740 750 760 762 782 800 CC 808 A7 810 811 815 815 W/B 828 912 918 919 925 975 980 1009 B 1010 1010 O 1010/0 1012 1013 1014 1017 1017 W 1018 1019 1021 1021 B 1022 1022 B 1023 1023 R 1025 1027 1037 1037 W 1065 1065 B 1068 1068 W 1070 1071 1072 1073 1073 W 1074 1074 W 1075 1075 W 1076 1076 W 2051 2085 2085 V 2207 2908 2908 V 2909 2910 2910 V 2911 2911 V 2912 2912 V 2913 2914 2915 2915 V 2916 2916 V 2917 2917 V 2918 2920 2920 V 2921 2922 2923 2923 V 2924 2924 V 2925 2925 V 2926 2926 V 2927 2927 B 2928 2930 2930 V 2931 2932 2940 2940 V 2941 2941 B 2942 2943 2945 2945 V 2946 2946 V 2947 2947 R 2948 2948 B 2949 2949 B 2950 2950 B 2951 2951 V 2952 2952 V 2953 2953 B 2954 2954 B 2955 2955 B 2956 2956 O 2957 2957 V 2958 2958 V 2959 2959 B 2960 2960 B 2961 2961 V 2962 2962 V 2963 2963 B 2964 2964 B 2965 2965 B 2966 2966 B 2967 2967 B 2968 2969 2970 2970 B 2971 2971 B 2972 2972 V 2973 2974 2980 2981 3071 4070 51122 51123 51132 51133 52124 53125 54145 55146 55427 56147 59201 59202 布 & 皿 neons flashing 閃 neon illuminated

A (190 codes)

A (number) A 01 A 02 A 03 A 18 A 36 A 37 A 39 A 40 A 41 A fault on gas supply A Flashing A Illuminated continuously A LED 1 A LED 2 A LED 4 A LED 5 A LED 6 A neon flashing A nn A short pulse every 4 seconds A xx A-1 A-2 A-4 A-5 A-6 A-A5 A-b2 A-b4 A(3) A0 A0:0 A0:1 A0:2 A1 A01 A1 281 A02 A2 A2:0 A2:1 A2:2 A03 A3 A3 317 A3:-9 to A3:15 A04 A4 A5 A05 A5:0 A5:5 A06 A6 A7 A07 A7 808 A8 A08 A8 (361) A8 362 A09 A9 A09-12 A10 A11 A12 A13 A14 A15 A16 A17 A18 A19 A20 A21 A22 A23 A24 A33 A36 A37 A39 A40 A41 A42 A51 A54 A54 – A55 – A63 A55 A56 A61 A62 A63 A63 / A64 / F66 A64 A68 A97 A98 A99 A1281 A3317 A8362 AA 0011 AA 0033 AA 7755 AA 7777 AA 9977 AA 9988 AA 9999 AA0011 AA0022 AA0033 AA0077 AA1199 AA2200 AA2211 AA2222 AA3333 AA9977 AA9988 AA9999 AC Activate BCC Ad ADC LOCKOUT AF AIR FLOW DEVICE Air flow fault Air Flow Monitor Air Flow Monitor Neon Air flow rate safety device AIR PRESSURE ERROR Air Pressure Fault Air Pressure neon Air Pressure O.K. AIR PRESSURE OK Air pressure switch AIR PRESSURE SWITCH N.O. Air pressure switch not proved Air Proving LOCKOUT AL10 AL20 AL21 AL26 AL28 AL34 AL40 AL41 AL52 AL55 AL60 AL71 AL73 AL74 AL74, AL79 AL79 Alert All Boilers All Lamps OFF All Lamps ON All LEDs Off All lights: OFF All neons flashing All operation lights OFF All Ultracom Amber LED illuminated Amber neon Amber neon (on panel) Amber neon lit An An 11 Anti-cycle ANTI-CYCLE DEVICE Anti-frost device ANTI-FROST DEVICE ACTIVATED anticycle APPLIANCE COMPLETELY SHUT DOWN APPLIANCE FIRES THEN LOCKOUTS Appliance stays fired Appliance wont fire APS Cycling LOCKOUT APS neon lit APS Stuck Fault AUTODIAGNOSIS FAULTY Autodiagnostics faulty Autofrostat Function Autofroststat mode Automatic Shutdown

B (204 codes)

b 18 b 19 b 24 b 25 b 26 b 28 b 29 b 30 b 33 b 38 b 61 b 65 B Flashing B Illuminated continuously B LED 1 B LED 2 B LED 3 B LED 4 B LED 5 B LED 6 B neon flashing B-1 B-2 B-3 B-4 B-5 B-6 B, C, D, E & F neons flashing b... b/E 18 b0 B1 B01 b2 B02 b2, b3, b4, b5,b6 b3 B03 b4 b5 B05 b6 B06 b7 B07 b7 257 b8 B08 b9 B17 b18 b19 b20 b22 b24 b25 b26 b28 b29 b30 b33 b34 b35 b43 b52 b52 °C b65 B7257 bA Bar LED Flashing Bat bb.. BC BCC error bd BE Below 1 bar Below Minimum Betacom Betacom c bF bL blank BLANK DISPLAY BLANK DISPLAY SCREEN Blinking RED Block 01 Block 11 Block 12 Block 60 Block 67 Block 80 Block 81 Block 82 Block 85 Block 86 Blocked Flue/Condensate Blocking Blocking Error Blue indicator (2) will flash Blue indicator light flashing Blue indicator light off Blue light Blue Light Flashing Blue light off Blue light on Blue light: Off / Lockout: Off Blue light: On / Lockout: Off Boiler at lock out Boiler controls Boiler Fault Finding 1 Boiler Fault Finding 2 Boiler Fault Finding 3 Boiler Fault Finding 4 Boiler Fault Finding 5 Boiler Fault Finding 6 Boiler Fault Finding 7 Boiler Fault Finding 8 Boiler Fault Finding 9 Boiler Fault Finding 10 Boiler Fault Finding 11 Boiler Fault Finding 12 Boiler lock out Boiler locked-out Boiler lockout Boiler lockout indicator ON Boiler locks out Boiler Model Boiler On Boiler ON (green) light off Boiler On (Orange LED) Boiler On light Boiler On light on Boiler On neon Boiler overheat BOILER OVERHEAT STAT TRIPPED Boiler overheat thermostat Boiler Safety Overheat neon BOILER SAFETY SHUTDOWN Boiler sensor BOILER SENSOR FAULT Boiler shut down (lock out) BOILER SHUTDOWN Boiler sooting Boiler Temperature Boiler temperature below 8°C Boilers Boiling Bottom red light bP BUBNEB STAYS ON Burner BURNER (FLASHING) Burner air ports blocked Burner does not ignite Burner fails to ignite Burner fails to light BURNER FAILS TO START Burner Failure BURNER FIRING 100% Burner goes out Burner indicator Flashing BURNER indicator Slow flash Burner LED Green BURNER LIGHT ONLY Burner Lit LED BURNER LIT NEON Burner lock indicator Burner lock out indicator Burner lock out neon Burner Lock-out Burner Lockdown Burner Lockout Burner Lockout A Burner Lockout B Burner Lockout C Burner Lockout D Burner Lockout E Burner Lockout F Burner lockout indicator (red) Burner malfunction indicator Burner motor fails to operate Burner Neon (Flashing) Burner not working Burner On Burner On (Green Light) Burner On (Green) light flash Burner On (Green) light on Burner ON LED (Green) Burner On light off Burner On Neon Burner ON neon (green) Burner On neon / Gas Valve On Burner On neon going out Burner on neon NOT illuminated Burner On neon off Burner output modulates Burner pulsates Burner pulses Burner shut-down BURNER Slow flash Burner starts, no flame BURNER STAYS ON bxx

C (136 codes)

C (Flashing) c 1 05 C 20 C 40 c 55 C 61 C 78 C LED 7 C neon flashing c OF C RY2 C RY4 C-7 C.h. operation C(1) C(2) C(3) C(4) C(5) C/H Sensor Fault C0 C1 C1 05 C1 10 C1 11 c1 17 c1 18 C1 29 C1 33 C1 51 c1 54 C1 264 C2 C3 C3 (ΔP-C) C4 C4 (237) C4 (ΔP-C) C4 273 C5 C5:20 C6 C6 215 C6 216 C6:75 C7 C7 214 C7 216 C7 217 C10 C12 C14 C15 C17 C18 C20 C21 C28 C40 c80 c80 °C C123 C1264 C2849 C4237 C4273 C6215 C6216 C7214 C7216 C7217 CA Case sensor Case temperature Casting Thermistor Fault CC (800) CC.. CC800 Cd CE CE 207 CE 266 CE207 CE266 Central Heating Active (Green) Central Heating LED flashing Central Heating NTC fault CF CF05 CH Fault CH flow sensor fault CH LED CH light flashing CH light On CH light On (flashing) CH light on PCB 40 flashing CH PUMP Fast flash CH PUMP indicator Fast flash CH PUMP indicator Slow flash CH PUMP Slow flash Check JP1 ci range Circulation Circulation LOCKOUT CO COdE code9 COMBUSTION FAN FAULT Communication fault Compact e / s Complaints of noise Complaints of noise (1) Complaints of noise (2) Complaints of noise (3) Complaints of noise (4) Complaints of noise (5) Complaints of noise (6) Complaints of noise (7) Complaints of noise (8) Complaints of noise (9) con Condensate Drain Blockage Condensate in boiler Condensate Pump (Green Light) Condensate pump failed CONDITION 1 CONDITION 2 CONDITION 3 Condition K Connection Connectivity Red Constant RED Control failed Control Satisfied cP CRC error

D (175 codes)

D neon flashing D,11 d.00 D.0 D.000 d.01 D.1 d.02 D.2 D.002 d.03 D.3 d.04 D.4 d.05 D.5 d.06 d.07 D.7 d.08 D.8 d.09 D.9 D.10 D.12 D.13 d.14 D.014 d.15 d.16 D.17 D.18 D.19 D.20 d.21 D.22 D.23 D.24 D.25 D.26 D.27 D.28 D.30 d.31 D.33 D.34 d.35 D.36 d.37 d.39 D.40 D.41 d.43 D.44 d.45 d.46 D.47 D.50 D.51 D.58 D.60 D.61 d.62 D.64 D.65 d.66 d.67 D.68 D.69 D.70 D.71 D.72 D.73 D.75 D.76 D.77 D.78 D.80 D.81 D.82 D.83 D.84 D.084 D.90 D.91 D.93 D.094 D.096 D.96 D.97 D.98 D.118 (1) D.118 (2) D.118 (3) D.118 (4) D.118 (5) D.118 (6) D.118 (7) D.118 (8) D.118 (9) D.118 (10) D.118 (12) D.118 (13) D.118 (14) D.118 (15) D.118 (16) D.h.w. operation d.xx d1 d1 & d2 D1 240 D1 241 D1 286 d2 d3 D3 232 d3:14 D4 D4 (341) D4 213 D4 271 D4 286 d4:0 d5 D6 d9 d10 D1240 D1241 D3232 D4213 D4271 D4286 D4341 dA db dd.. dE Demand DEMAND LIGHT ONLY DEMAND NEON Detection Fault DETECTION LOCKOUT DHW Fault DHW FLOW SWITCH DHW Flow Switch section DHW light DHW NTC fault DHW pump DHW PUMP (FLASHING) DHW PUMP Fast flash DHW PUMP indicator Fast flash DHW PUMP indicator FLASHING DHW PUMP indicator Slow flash DHW PUMP Slow flash DHW sensor fault DHW SENSOR LOCKOUT DHW Thermistor Fault Digital control system Display Flashing Display not illuminated Does fan Hunt? (YES) Does fan run? (NO) Does main burner light? (NO) Does pilot light? (NO) DOMIcondens HE 26 C Double flash Blue light DOWNDRAUGHT FAULT dP DRIFT TEST WAITING Dry fire sensor Dry-Fire DRY-FIRE LOCKOUT Dry-Fire section dU

E (632 codes)

E (number) E 00 E 02 E 03 E 04 E 05 E 06 E 07 E 08 E 09 E 10 E 11 E 12 E 13 E 14 E 15 E 16 E 17 E 18 E 19 E 20 E 22 E 23 E 25 E 26 E 27 E 28 E 29 E 30 E 31 E 32 E 33 E 34 E 35 E 36 E 37 E 38 E 44 E 60 E 61 E 65 E 94 E 95 E 99 E neon flashing E-01 E.00 – .04 E.00 – .05 E.01 – .02 E.01 – .04 E.01 – .11 E.01 – .12 E.01 – .17 E.01 – .20 E.02 – .00 E.02 – .07 E.02 – .16 E.02 – .17 E.02 – .19 E.02 – .20 E.02 – .21 E.02 – .47 E.02 – .48 E.04 – .00 E.04 – .01 E.04 – .02 E.04 – .03 E.04 – .04 E.04 – .05 E.04 – .06 E.04 – .08 E.04 – .10 E.04 – .12 E.04 – .13 E.04 – .17 E.782 E0 E00 E00 to E99 E00-684 E00-688 E00-711 E00-716 E00-720 E00-721 E00-722 E00-730 E00-737 E00-738 E00-741 E01 E1 E001 E01 + RESET E01 075 E01 373 E01 412 E01 530 E01 540 E01 553 E01---204 E01---205 E1-64 E1-65 E1-66 E1-67 E1-68 E1-69 / E1-70 E1-71 E1-72 E1-73 E01-074 E01-156 E01-372 E01-374 E01-490 E01-505 E01-507 E01-840 E02 E2 E002 E02 + RESET E02 026 E02 071 E02 078 E2 222 E2 223 E2 233 E2 350 E2 351 E03 E3 E003 E03 + RESET E03 818 E03-884 E03-885 E03-886 E03-887 E03-888 E03-893 E03-894 E04 E4 E004 E05 E5 E005 E05 070 E5 218 E5 332 E06 E6 E07 E7 E08 E8 E09 E9 E9 210 E9 219 E9 220 E9 221 E9 224 E9 276 E9 277 E9 285 E9 318 E10 E10 + RESET E11 E011 E12 E012 E12 to E22 E13 E13/16/19 E14 E14 + RESET E15 E15v E16 E016 E16, E17, E18 E17 E18 E19 E20 E020 E20 + RESET E21 E21 + RESET E22 E22 + RESET E23 E23 + RESET E24 E24 + RESET E25 E25 + RESET E26 E26 186 E26 219 E26 221 E26 392 E26 398 E27 E28 E29 E30 E030 E31 E031 E32 E33 E34 E35 E36 E37 E38 E39 E40 E040 E41 E041 E42 E042 E43 E44 E45 E46 E046 E47 E047 E48 E49 E50 E51 E52 E53 E54 E55 E56 E056 E57-048 E57-049 E058 E58 E060 E60 E62 E63 E64 E65 E065 E66 E68 E69 E69-243 E70 E72 E73 E74 E75 E76 E77 E077 E78 E79 E80 E080 E80-450 E80-451 E83 E83---121 E83---129 E83---178 E83---180 E83---181 E83---196 E83---197 E83-013 E83-081 E83-082 E83-086 E83-101 E83-122 E83-126 E83-127 E83-142 E83-145 E83/E84/E85/E86/E87 E84 E85 E085 E085, E094, E095 E086 E86 E87 E89 E090 E90 E90-627 E091 E91 E92 E93 E094 E94 E95 E095 E96 E97 E98 E99 E100 E109 E110 E117 E118 E119 E121 E125 E127 E128 E129 E130 E131 E132 E133 E134 E135 E144 E151 E152 E153 E154 E157 E160 E160 / E161 E161 E162 E163 E164 E167 E168 E193 E205 E218 E270 E278 E279 E291 E302 E317 E321 E351 E352 E353 E384 E385 E407 E421 E430 E432 E434 E439 E441 E445 E480 E515 E517 E593 E594 E595 E596 E598 E615 E00716 E736 E740 E761 E762 E773 E777 E782 E783 E784 E785 E786 E787 E788 E792 E01612 E2222 E2223 E2233 E2350 E2351 E5218 E05233 E05234 E9210 E9219 E9220 E9224 E9276 E9277 E9285 E9318 E83458 E83462 E83465 E83466 E83467 E83468 E83476 E83477 E83481 E83482 E83483 E83484 E83485 E83486 E83488 E83489 E83491 E85739 E85740 E85752 E85753 E85761 E85762 E85802 E85901 EA EA 227 EA 229 EA 234 EA 261 EA 269 EA227 EA229 EA234 EA261 EA269 Earth Fault or Mains Reversal EC EC 256 EC256 ECO ECO-button flashes ECO-button flashing ECO-button lit ECO-button not lit ED EE 0044 EE 0055 EE 0066 EE 0077 EE 0088 EE 0099 EE 1100 EE 2200 EE 3300 EE 3311 EE 3333 EE 3344 EE 8800 EE 9944 EE 9955 EE 9999 EE1 EE2 EE3 EE4 EE5 EE6 EE8 EE9 EE0022 EE0033 EE0044 EE0055 EE0066 EE0077 EE0088 EE0099 EE2200 EE2211 EE2222 EE2233 EE3333 EE3344 EE5566 EE6644 EE6666 EE7744 EE9999 EEPROM LOCKOUT EF EF 349 EF349 EH EH (258) EH258 EL Electrical Supply Fault Electrode does not spark Enn EP Er ER + 14 + Reset ER + 25 + Reset ER + 69 Er 01 ER 01 + Reset Er 02 ER 02 + Reset Er 03 ER 03 + Reset Er 04 ER 04 + SPANNER Er 05 ER 05 + RESET Er 06 ER 06 + SPANNER Er 07 ER 07 + SPANNER Er 08 ER 08 + SPANNER Er 09 ER 09 + SPANNER ER 10 + reset Er 11 + RESET ER 12 + SPANNER ER 14 + SPANNER ER 15 + RESET ER 16 + RESET ER 17 + RESET ER 18 + RESET Er 19 ER 19 + SPANNER ER 20 + SPANNER Er 25 ER 69 + SPANNER Er 99 Er.1 Er.2 Er.3 Er.4 Er.5 Er.6 Er.7 Er.8 Er.9 Er.10 Er.11 Er.12 Er.13 Er.14 Er.15 Er.16 Er.17 Er01+RESET Er02+RESET Er03+RESET Er04+ Er05+ Er06+ Er07+ Er08+ Er09+ Er10+RESET Er11+RESET Er14+ Er14+RESET Er18 Er99 Err Err / 108 Err / 110 Err.1 Err.2 Err.3 Err.4 Err.5 Err.L Err.L - Err.5 ERR>07 ERR>CM Erroneous APS signal ERROR Error 00 Error 01 Error 01 + RESET Error 02 Error 03 Error 04 Error 05 Error 12 Error 18 Error 19 Error 20 Error 28 Error 50 Error 69 Error 80 Error 110 Error 119 Error 125 Error 130 Error 133 Error 160 Error 193 ERROR CODE 1 ERROR CODE 2 ERROR CODE 3 ERROR CODE 4 ERROR CODE 5 ERROR CODE 6 ERROR CODE 7 ERROR CODE 8 Error in power supply Escape of Gas Excessively noisy burner Excessively noisy burner (1) Excessively noisy burner (2) Excessively noisy burner (3) EXHAUST SENSOR FAULT Explosive ignition

F (520 codes)

F (Flashing) F (High system water pressure) F (Ignition fault shown) F (Low system water pressure) F 0A F 0t F 0U F 04 OR L 04 F 05 OR L 05 F- F-15 F.00 F.0 F.00 / F.0 F.01 F.1 F.01 / F.1 F.02 F.03 F.4 F.5 F.6 F.10 F.11 F.12 F.13 F.17 F.20 F.21 F.22 F.23 F.24 F.25 F.26 F.27 F.28 F.29 F.32 F.33 F.35 F.37 F.41 F.42 F.43 F.49 F.55 F.56 F.57 F.60 F.60 to F.67 F.61 F.62 F.63 F.64 F.65 F.66 F.67 F.68 F.70 F.71 F.72 F.73 F.74 F.75 F.76 F.77 F.78 F.80 F.81 F.82 F.83 F.84 F.85 F.86 F.87 F.88 F.89 F.90 F.91 F.92 F.94 F.97 F.XX F.XX-F.XX F/R ∆T = 45°C F0 F00 F000 F0 (238) F0 (239) F0 (242 - 256) F0 (258) F0 (262) F0 (272) F0 (290) F0 237 F0 237-239 F0 242 F0 259 F0 263 F0 267 F0 278 F0 279 F0 280 F0 287 F0 338 F0 d F1 F01 F001 F1 (259) F1 (263) F1 or F4 F1, F4 F2 F02 F002 F2 or Fn or Ln F2, FN or LN F3 F03 F003 F4 F04 F004 F04 L04 F4 Or L4 F5 F05 F005 F05 L05 F5 Or L5 F5/F9 F6 F06 F006 F7 F07 F007 F07 – F14 – A07 F7 228 F7 328 F8 F08 F008 F08 – A08 F9 F09 F009 F09 – A09 F09 L09 F9 or L9 or F8 or L8 F9 to F0 F9, L9, F8 or L8 F10 F010 F10 – A10 F10 to F22 F10-F22 F11 F011 F11 – A11 F12 F012 F13 F13 – A13 F14 F014 F15 F015 F16 F016 F17 F18 F018 F19 F019 F20 F21 F22 F23 F24 F25 F26 F27 F027 F28 F028 F29 F029 F30 F030 F31 F031 F32 F33 F34 F35 F36 F37 F38 F39 F40 F41 F42 F42 – A42 F43 F44 F45 F46 F47 F49 F50 F51 F52 F53 F56 F56 – A56 F61 F61 – A61 F62 F63 F64 F65 F66 F67 F68 F68 – A68 F70 F71 F72 F73 F74 F75 F76 F77 F81 F83 F84 F85 F86 F0237 F0238 F0239 F0242 F0258 F0262 F0272 F0278 F0279 F0280 F0287 F0290 F1259 F1263 F7228 F7328 FA FA 306 FA 364 FA9 FA306 FA364 FAIL POINT A FAIL POINT B FAIL POINT C FAIL POINT D FAIL POINT E FAIL POINT F FAIL POINT G FAIL POINT G Primary Overheat FAIL POINT H FAIL POINT H / Burner Lockout FAIL POINT I FAIL POINT I / Sensor Fault FAIL POINT J FAIL POINT K FAIL POINT L FAILED PELLET LIGHTING Failure at point A Failure at point B Failure at point C Failure at point E Failure at point G Failure at point K Failure at point L FAILURE AT POINT M FAILURE AT POINT N Failure at point O Failure at point P Failure at point Q FAILURE AT POINT S FAILURE TO LIGHT False Flame Fault FALSE FLAME LOCKOUT FAN Fan (If fitted) Fan does not run Fan does not run at max speed Fan doesn't turn Fan Error Fan Failure Fan Fault Fan Hunt Fan hunts Fan Lockout FAN NEON Fan not running Fan On Fan operates / No spark Fan operation indicator Fan or Flue Fault Fan Overrun Fan Purge Fan rpm not exact Fan runs Fan runs at max. speed Fan runs boiler does not work Fan speed Fan turns Fan/Flue LED Green Fast flash Fast flash (Reset button Off) Fast flash / Flashing Fast flash / Not a fault code Fast flash / Off Fast flash, Lockout reset: Off Fast Flashing Fast Flashing (8Hz) Fast flashing reset button Fault Fault 01 / 200 Fault 01 / 201 Fault 02 / 40 Fault 02 / 42 Fault 02 / 43 Fault 02 / 100 Fault 02 / 205 Fault 02 / 255 Fault 03 / 20 Fault 03 / 21 Fault 11 / 131 Fault 11 / 132 Fault 12 Fault 12 / 170 Fault 12 / 171 Fault 13 / 157 Fault 13 / 158 Fault 13 / 159 Fault 14 / 117 Fault 14 / 118 Fault 14 / 119 Fault 15 / 30 Fault 19 / 202 Fault 20 / 193 Fault 29 / 202 Fault 30 / 7 Fault 33 / 22 Fault 40 / 101 Fault 40 / 102 Fault 41 / 103 Fault 41 / 104 Fault 50 Fault 50 121 Fault 50 126 Fault 50 140 Fault 51 122 Fault 51 123 Fault 51 127 Fault 51 132 Fault 51 133 Fault 52 124 Fault 53 125 Fault 53 128 Fault 54 Fault 54 145 Fault 55 146 Fault 56 147 Fault 56 154 Fault 59 201 Fault 59 202 fault condition Fault Condition 11 Fault finding (Page 9 - 10) Fault Image Fault indication Fault indication light (2) Fault led (B) illuminated Fault light is on Fault on gas feeding Fault on gas supply FAULT POINT A FAULT POINT B FAULT POINT C FAULT POINT D FAULT POINT E FAULT POINT F Faulty air pressure sensor Faulty air pressure switch Faulty CH thermistor Faulty condensate drainage Faulty flame detection Faulty gas valve Faulty ignition Faulty ignition device Faulty modulation gas valve Faulty primary circuit Fb Fb 365 FB365 FC FC1 FD FD 231 FD231 FE FE94 FE95 FE96 FE97 FH fI- Fig. 14 Fig. 15 Fig. 16 Fig. 17 FILL FILL (continuous) FILL (flashing) Filling Fixed red LED fl- Flame FLAME CIRCUIT FAILURE FLAME Detected Flame detected after gas Flame detection error Flame detection fault Flame does not persist Flame Failure Flame Failure (Red Light) Flame Failure (Red Light) ON FLAME FAILURE LED Flame Failure Neon flame failure reset Flame Failure Reset Button Flame failure: lock out Flame indicator Flame indicator (yellow) flame lock-out Flame loss Flame On Before Gas On Flame On Before Gas Valve On Flash Flash 4 times per second Flash 8 times per second FLASH FLASH ON FLASH OFF FLASH FLASH OFF ON FLASH ON FLASH FLASH ON ON Flash once per second Flashes red Flashes red/green FLASHING Flashing 0.3 bar FLASHING 2 Per Sec. Flashing 30 Flashing 40 Flashing 50 Flashing 60 Flashing 70 Flashing 80 Flashing 90 flashing FILL / HIGH Flashing Green Flashing lamp Flashing LD1 Flashing LD2 Flashing light Flashing mains LED Flashing Mains ON light Flashing pressure Flashing Red Flashing red A or B Flashing Red LED Flashing yellow Float switch Float switch (if fitted) floor thermostat contact open Flow Flow return reversed Flow sensor Flow Switch Flow temperature low Flow Thermistor Flow Thermistor Fault FLOW/RETURN SENSOR DRIFT ERROR Flue blockage Flue gas overheat Flue gas pressure switch Flue gas sensor faulty Flue overheat FLUE OVERHEAT THERMOSTAT FLUE SENSOR Flue Spillage Fault Flue temperature probe lockout FLUE TEMPERATURE SENOR LOCKOUT Fn FO FO30 FP Frequent sooting (1) Frequent sooting (2) Frequent sooting (3) Frequent sooting (4) Frequent sooting (5) Frost protect operation FU fuse blown

G (59 codes)

G2 G5 G9 GAS CONTROL TAP STIFF (USER’S) GAS CONTROL TAP STIFF (USERS) Gas injectors blocked Gas injectors plugged Gas On Gas supply fault GAS TAP STIFF GAS VALVE FAULT GAS VALVE NOT OPENING Gas valve(s) Good Grant Fault GREEN Green - continuous Green 'Flame' led Green 'Running' light Green | On every 0.5 second GREEN blinking GREEN blinking (0.5s) Green blinking light Green LED GREEN LED BLINKS Green LED flashing Green LED illuminated Green LED Off, Red LED Off Green LED OFF, Red LED ON Green LED on GREEN LED ON every 0.5-secs GREEN LED ON every 6-secs Green LED ON, Red LED OFF Green LED On, Yellow LED On Green LED On/flashing GREEN LED Solid Green Light Green light 'On' only Green light flashes rapidly Green light flashing slowly Green light On continuously Green neon GREEN ORANGE blinking (0.5s) Green zone; end of green zone Green/Red - blinking Green/Red flashing Group 1 Group 1, 1 flash Group 1, 2 flashes Group 1, 3 flashes Group 1, 4 flashes Group 1, 5 flashes Group 2 Group 2, 6 flashes Group 2, 7 flashes Group 2, 8 flashes Group 2, 9 flashes Group 2, 10 flashes Group 3

H (98 codes)

H 1 H 2 H 3 H A H A (flashing) H E H F H n H-- H.....4...... H.01 – .00 H.01 – .05 H.01 – .08 H.01 – .14 H.01 – .18 H.01 – .21 H.02 – .02 H.02 – .03 H.02 – .04 H.02 – .06 H.03 -.00 H.03 – .01 H.03 – .02 H0 H1 H2 H2o H03 H3 H4 H5 H6 H07 H7 H8 H08 H9 H09 H9-01 H9/L9 H11 H12 H13 h13/H13 H20-986 H21-048 H21-049 H21-052 H21-060 H21-064 H27-582 H29 H00266 H00269 HA Halo screen shows Replace Halo Hb HC HC-01 Hd HE HE DHW OUTLET SENSOR Heat exchanger overheat Heatbank Overheat Stat HEATING BODY NOISE HEATING BODY VOISE Heating demand light OFF Heating demand light ON Heating LED (Green) Heating system HF HHHHH:::::AAAAA HIGH High limit High Limit Thermostat (Yellow) High neon light High Pressure Fault High Pressure Sensor Error HIGH SMOKE NUMBER HIGH WATER FLOW HIGH WATER FLOW RATE HIGH WATER TEMPERATURE HJ-08 HJ-09 HJ-10 Hn Hot Surface Igniter Hot Water Active (Green) Hot water demand indicator Hot water high limit stat Hot Water LED (Green) hp HP Comms No illumination HrE HW light flashing HW light On (flashing) HW light on PCB 40 flashing hxi range

I (52 codes)

J (23 codes)

J01 J2E J3E J5E J6-01 J6-20 J6-21 J6E J11 J12 J31 J32 J43 J45 J46 J47 J52 J61 J65 JJ-64 JP6 JP8 JP9

K (1 codes)

L (297 codes)

L (Flashing) L 0C L 0d L 8 L A L A (flashing) L E L F L F (flashing) L- L-01 L.....E...... or H.....E...... L.E.D. B L.E.D. D L.E.D. E (Yellow) L.E.D. G L.E.D. H (Yellow) L.E.D. I L.E.D. I (Red) L0 L1 L01 L1E L2 L02 L2E L3 L3E L4 L04 L4 or F4 L5 L05 L5 or F5 L5E L6 L06 L6E L7 L8 L9 L09 L11 L12 L31 L32 L34 L43 L45 L46 L47 L52 L61 L65 LA LA/HA Lack of burner ignition Lamps flashing LB7 LBC LBE LC LC1 LC2 LC3 LC4 LC5 LC6 LC7 LC8 LC9 LCA LCB LCD LCE Ld LD1 LD1, LD2 Flashing LD1, LD2, LD3 Flashing LD2 LD2, LD3 Flashing LD3 LD3 ON LD4 LE LED 1 LED 1 (RESET) Constant Light LED 1 Fast Flashing (8Hz) LED 1 fast pulse LED 1 green (0) LED 1 ON (RESET) LED 1 Slow Flashing (2Hz) LED 1-2-3-4 (◯◯◯●) LED 1: 0 LED 1: Off, LED 2: On LED 1: On, LED 2: Off LED 1: On, LED 2: On LED 2 LED 2 (A) LED 2 (B) LED 2 (C.H.) LED 2 (CH) LED 2 (D.H.W.) LED 2 (DHW) LED 2 Burner Lit LED 2 Fast Flashing (8Hz) LED 2 goes OFF LED 2 OFF LED 2 OFF briefly LED 2 ON LED 2 ON (BURNER LIT) LED 2 on P.C.B. alight LED 2 on PCB 41 lit LED 2 Slow Flashing (2Hz) LED 2 yellow (0) [DHW mode] LED 2 yellow (1) [CH mode] LED 2: 0 LED 2: 1 LED 3 LED 3 (B) LED 3 (CH) LED 3 lit LED 3 OFF (DHW Mode) LED 3 yellow (0) [CH mode] LED 3: 0 LED 4 LED 4 (A) LED 4 (B) LED 4 (C.H.) LED 4 (CH) LED 4 (D.H.W.) LED 4 (DHW) LED 4 (Flashing light) LED 4 (Flashing) LED 4 (Permanent light) LED 4 (Permanent) LED 4 flash/second LED 4 Flashing (DHW Mode) LED 4 green (0) [CH mode] LED 4 green (0) [DHW mode] LED 4 lit LED 4: 0 LED 4: 0 (Central Heating) LED 5 LED 5 (A) LED 5 (B) LED 5 (CH) LED 5 (DHW) LED 5 (Flashing light) LED 5 (Flashing) LED 5 (Permanent light) LED 5 (Permanent) LED 5 bar (Flashing light) LED 5 bar (Permanent light) LED 5 ON LED 5 red (1) [CH mode] LED 5 red (1) [DHW mode] LED 5: 1 LED 5: 1 (Central Heating) LED 6 LED 6 (A) LED 6 (B) LED 6 (C.H.) LED 6 (CH) LED 6 (D.H.W.) LED 6 (DHW) LED 6 yellow (0) [CH mode] LED 6 yellow (0) [DHW mode] LED 6: 0 LED 6: 0 (Central Heating) LED 7 LED 7 green (0) LED 7: 0 LED 8 yellow (0) LED Flashing LED off LED1 LED1 flashing, LED2 on LED1 on LED1 on, LED2 flashing LED2 LED2 flashing, LED3 on LED2 on LED2 on PCB 37 LED3 LED3 on LED3 on PCB 37 LED4 LED4 flashing LED4 permanent LED5 (Permanent) LED5 bar (Flashing) LED5 flashing LED5 on LF Lh Li Li 01 Li01 Light off Light on Lights On Off On Lights On On On Lights: Flash, Flash, On Lights: Flash, Off, Flash Lights: Flash, Off, On Lights: Flash, On, Flash Lights: Flash, On, On Lights: Off, Off, Off Lights: On, Flash, Flash Lights: On, Flash, On Lights: On, Off, Flash Lights: On, On, Flash Limescale Build-up Limit stat tripped Live & Neutral Reversed LLLLL ::::: FFFFF LLLLL:::::AAAAA Ln LO2 Lock lamp / lock state Lock lamp on Lock Out After 15 Seconds Lock out radiator light Lock state Lock state cause lock-out Lock-out (Flashing light) Lock-out (light on) Lock-out (Red neon) Lock-out (Steady light) Lock-out Indicator Lock-out lamp lock-out light Lock-out reset button is lit Lock-out reset button lit lock-out signal lamp Lock-out signal lamp D blinks Lock-out signal lamp E blinks Lock-out signal lamp OFF Lock-out signal lamp ON Lock-out signal lamp red Lock-out signal lamp red (ON) Lock-out state lockout Lockout (LED Mode) Lockout (Rapid Flashing Red) Lockout (rapid flashing) Lockout (Red LED) Lockout (Red) Lockout (Red) flashing Lockout (Red) light flash Lockout (Red) light is on Lockout (Red) light on Lockout (Red) light will flash Lockout (Red) On Lockout button lit Lockout flame signal Lockout lamp (red) on Lockout LED lockout LED 2 ON Lockout LED continuously on Lockout light Lockout light (constant) Lockout light constantly on LOCKOUT LIGHT FLASHING Lockout light illuminated Lockout light on LOCKOUT LIGHT ON CONSTANTLY Lockout will not reset LOCKOUT: a LOCKOUT: b LOCKOUT: c LOCKOUT: d Locks Out In Morning Only Loss of system water pressure Loss of water indicating light Low Electrical Supply Low mains voltage Low neon light LOW POWER SUPPLY FROM MAINS Low Pressure Error LOW PRESSURE indicator lit Low system pressure Low System Pressure light Low system pressure neon lit Low system water pressure Low water pressure Low water pressure LED Low water pressure LED flash Low water pressure light ON LOW WATER SWITCH LOW WATER TEMPERATURE low-pressure Low-pressure fault code LP Lt

N (141 codes)

neon '12' illuminated Neon 1 Neon 1 lit Neon 1 lit (No) Neon 1 NOT lit Neon 2 Neon 2 lit Neon 2 lit (No) Neon 2 NOT lit Neon 3 Neon 3 lit Neon 3 lit (No) Neon 3 NOT lit Neon 4 Neon 4 lit Neon 4 lit (No) Neon 4 NOT lit Neon 5 Neon 6 Neon 7 Neon 8 Neon 9 Neon 10 Neon 11 Neon 24 Neon 25 Neon 26 Neon 27 Neon 28 Neon 29 Neon A Neon A flashing Neon B Neon B flashing Neon B Flashing very slowly Neon C Neon C illuminated Neon D Neon D illuminated Neon D NOT illuminated neon flashing neon flashing (1st instance) neon flashing (2nd instance) neon flashing (3rd instance) neon flashing (4th instance) neon flashing (5th instance) neon flashing (Fan) Neon flashing (Generic) neon flashing (Overheat) neon flashing (Section B) neon flashing (Section B/C) neon flashing (Section C) neon flashing (Section D) neon flashing (Section E) neon flashing (Section F) neon flashing (Section H & K) neon flashing (Section I) neon flashing (Section I/M) neon flashing (Section J) neon flashing (Section J/M) neon flashing (Section M) neon flashing (Spark/Ignition) neon I 1 neon I 2 Neon I3 Neon illuminated (Burner) Neon l1 Neon l2 Neon l3 Neon L4 Neon L5 Neon L6 Neon SG Neon SG1 Neon SGI Neon1 Neon2 Neon3 Neon4 NEON5 Neon6 Neon7 Neon8 Neon9 neons flashing (Section D) nF1 No burner ignition No CH function (DHW OK) NO CH OPERATION No code NO CODE 212 No code 213 No code 260 No code 380 No code displayed NO DHW BUT CH ON No DHW But CH Works OK No DHW function (CH OK) No DHW temperature control No display No display, boiler inactive No display, boiler working OK No display, pump running NO FAN No Fan Run No flash No flow No fuel supply No functions No illumination (HP Comms) No LED No light No light / Not a fault code No lightindication No lights NO LIGHTS AT ALL No lights on no line supply on violet lead no live supply on red lead NO LOCKOUT RESET No mains LED No neon illuminated No oil from nozzle NO OR LOW WATER FLOW RATE No Pump Feed No spark at electrode No spark at ignition electrode No Switched Live No Water Flow NO WATER L.E.D. no. 46 no. 47 no. 48 Noise Noises in CH system NOISY HEATER Noisy Ignition Noisy operation None Normally operating boiler NOT OPERATING IN HEATING MODE

O (88 codes)

OC OF OFF Off (No light) Off / Off OFF OFF OFF Oil odours OIL SMELLS ON On * On Off On / Off On / Off (CH fault) On / Off (Demand fault) On / Off (General fault) On / Off (HW fault) ON FLASH FLASH ON FLASH ON On Off * Off ON OFF FLASH ON OFF ON On Off On Off On Off On Off * * On On ON ON FLASH ON ON ON On On On On Operation lights flashing OPn OPTIMAX HE PLUS 38C ORANGE Orange 'Mains' light ORANGE blinking Orange LED Orange LED on Orange Light Orange light (Boiler fault) Orange light (first) Orange light (second) Orange light (single) Orange light (third) ORANGE steady ON OT ERROR Other Codes Other defects OTHER FAULTS OUTDR Outlet sensor faulty Outside sensor Outside sensor (if fitted) OUTSIDE SENSOR FAULT Over temperature Overcurrent Protection Error Overheat Overheat - Red LED: FLASHING Overheat 'stat trip Overheat 'stat tripped Overheat (Red LED) Overheat condition OVERHEAT CUT-OFF Overheat Detection OVERHEAT FAULT OVERHEAT HIGH LIMIT Overheat indicator Overheat indicator light Overheat LED Overheat LED flashing Overheat LED illuminated Overheat light Overheat light on Overheat Limit Thermostat overheat lock-out state Overheat Lockout Overheat lockout indicator Overheat Neon Overheat Neon Illumination OVERHEAT PROTECTION TEST Overheat Stat neons flashing overheat stat trips Overheat thermostat Overheat thermostat (240XE) Overheat thermostat (240XP) Overheat thermostat activated Overheat Thermostat Cutout Overheat thermostat lockout Overheat Thermostat operates Overheat thermostat trip Overheating Overheating safety Override Green (flashing)

P (187 codes)

P (flashing) P (ΔP-V) p < 0.5 P 0.4 P 0.9 p 1.5 P 3.1 P 3.1 or higher P x.x P? P.00 P.0 P.01 P.1 P.02 P.2 P.3 P.03 P.4 P.04 P.5 P.06 P.6 P.07 P.11 P.12 P.13 p[ xx P00 P0 P0.1-0.4 P0.1-0.4 bar P0.5-0.9 P0.5-0.9 bar P1 P1, P2, P3 P1, P2, P3, P1... P1, P2, P3, P4 P1.0-2.9 P1.0-2.9 bar P2 P3 P3.0-3.5 P3.0-3.5 bar P4 P5 P6 P06 P06 00 P06 01 P06 02 P7 P8 P11 P12 P13 P19 P20 P21 P27 P33 Pb PC PCB 38 CH light flashing PCB 38 HW light flashing PCB Fault PCB REPLACED Pd PELLET FEED TUBE STAT TRIPPED Peripheral / Pump LED Green Permanent Live Permanent Live 'On' PH Pictogram of a spark Pilot being extinguished Pilot does not light Pilot does not remain alight Pilot extinguished PILOT FLAME DOES NOT LIGHT Pilot goes out Pilot On Pilot On light Pilot On light on PILOT WILL NOT LIGHT Pilot will not light (1) Pilot will not light (2) Pilot will not light (3) PILOT WILL NOT STAY ALIGHT PILOT WILL NOT STAY ALIGm Pilot/Ignition LED Green PO POINT B POINT C POINT D POINT E POINT F POINT G POINT H POINT I POINT J POINT K POINT L POINT M POINT N Poor performance / noises POOR PILOT FLAME power Power Failure POWER LED Power LED Green Power Neon (Flashing) Power On Power On (Green LED) Power ON (Green LED) blinking Power on indicator Power on indicator (green) Power On LED Power ON LED (Green) Power ON LED (Green) blinking Power On Neon Power supply PP/-- PP/AA PP/LL PP1 PP2 PP3 PP4 PP5 PP6 PP7 Pr 29 Pr 30 Pr00 Pr12 Preheat control neon flashing Preheat neon flashing Pressure < 0.5 bar Pressure 3 or greater Pressure below 0.5 Pressure below 0.5 bar Pressure below 1 pressure difference < 0.9 mbar Pressure fall below 0.5 BAR Pressure Gauge (below 0.5 bar) Pressure Gauge 3 or greater Pressure Gauge above 3 bar Pressure Gauge below 0.2 Pressure Gauge below 0.5 Pressure Gauge below 1 Pressure Gauge below 1 bar Pressure gauge D < 0.5 bar Pressure Gauge exceeds 3 bar Pressure Gauge J < 0.5 bar Pressure of 3 or greater PressureGauge < 0.5 BAR Primary flow switch operated Primary Overheat PROBE FAULT Pulsation on start Pulse Red (1 flash) Pulse Red (2 flashes) Pulse Red (3 flashes) Pulse Red (4 flashes) Pulse Red (5 flashes) Pulse Red (6 flashes) Pump Pump antiseize Pump circulating water / No Pump does not run Pump does not stop Pump Dry Run Pump failure PUMP FAULT Pump Fault or Low Pressure PUMP FED PUMP FEED Pump not running Pump over run thermostat 87˚C Pump Overrun - Central Heating Pump Overrun - Storage Tank Pump overrun thermostat fault PUMP PROTECTION ACTIVATED Pump rotor blocked Pump runs PUMP SAFETY DEVICE ACTIVATED Pump/Low Pressure Neon

Q (1 codes)

R (137 codes)

r1 r2 Radiators cold in winter Rapid flashes rE rE02 rE06 rE07 rE08 rE28 rE41 rE44 rE72 rE80 rE81 rE82 rE88 rE98 rE99 Red - blinking Red - continuous Red 'Flame Failure' neon lit Red (Connectivity) RED & GREEN lights flashing RED & GREEN lights OFF Red | On every 0.5 second Red | On permanently red ● Red B L.E.D. RED blinking (0.5s) Red blinking light Red D L.E.D. RED fast blinking RED fast blinking (0.2s) Red Flame Failure Indicator RED flashing (Reset button) Red flashing light Red flashing light (Flue) Red flashing light (Gas) Red flashing running lamp Red G L.E.D. Red indicator Red indicator (22) Red indicator 29 Red indicator illuminates Red indicator lit Red L.E.D. B Red L.E.D. D Red L.E.D. G Red L.E.D. H Red L.E.D. I Red L.E.D. I (Overheat) Red L.E.D. I illuminated Red LED Red LED (illuminated) Red LED (Lockout) Red LED (Overheat) Red LED (TTB) RED LED BLINKS Red LED five flash sequence Red LED flashing Red LED I Red LED I (Overheat) Red LED illuminated (Lockout) Red LED illuminated (Overheat) Red LED illuminated (TTB) Red LED is 'ON' RED LED LIGHT Red LED On RED LED on continuously RED LED ON every 0.5-secs Red LED on only Red LED on/Flashing Red LED Out (Lockout) Red led permanently on Red LED rapid flashing RED LED Solid Red LED two flash sequence Red LED: Flashing Red Red light Red light (Egg timer symbol) Red light (flashing) Red light F ON Red light flashes Red light flashing (Lockout) RED LOCKOUT BUTTON Red lockout indicator Red lockout indicator bulb Red lockout indicator bulb 29 RED lockout led Red lockout light red lockout neon Red lockout neon (lit) Red neon Red neon (A) flashing Red neon (on panel) Red neon illuminated Red neon light Red neon lit Red neon on fascia Red neon on fascia illuminated Red operational light 2 (E) Red reset button illuminated Red reset neon (lit) Red steady on red zone RED, GREEN blinking inverted RED, ORANGE blinking inverted Relay 2 energised after 2 sec REMOTE RESET LOCKOUT Repeated ignition failure Reset Reset Button Illuminated Reset LED is lit Reset light Reset Light (Ignition) Reset light (illuminated) Reset Light / Overheat Reset light is on Reset light on Reset neon Reset Neon (Flashing) Reset neon does not extinguish Reset neon illuminated (Red) Reset neon lights Return sensor Return sensor faulty Return Thermistor Return Thermistor Fault Reversed Polarity Reversed Polarity 'Off' RL2/RLX (not energised) Room Thermostat Fault RY2 RY2 Not Energised RY4 RY4 Not Energised

S (177 codes)

S 80 S.00 S.0 S.01 S.1 S.02 S.2 S.03 S.3 S.04 S.4 S.05 S.5 S.06 S.6 S.07 S.7 S.08 S.8 S.09 S.10 S.11 S.13 S.14 S.15 S.16 S.17 S.19 S.20 S.21 S.22 S.23 S.24 S.25 S.26 S.27 S.28 S.29 S.30 S.31 S.32 S.33 S.34 S.35 S.36 S.37 S.39 S.40 S.41 S.42 S.46 S.52 S.53 S.54 S.55 S.56 S.57 S.58 S.59 S.61 S.62 S.63 S.76 S.85 S.86 S.88 S.90 S.91 S.92 S.93 S.95 S.96 S.97 S.98 S.99 S.108 S.109 S.O S3 S9 S13 Safety disconnection (General) SAFETY HIGH LIMIT THERMOSTAT Safety indicator (4) lights Safety limit stat Safety LOCK-OUT Safety Lock-out LED SAFETY LOCKOUT Safety Lockout (Red LED) Safety lockout LED Safety Lockout LED (Red) Safety overheat device tripped Safety shut-down Safety Shut-off Safety system failure Safety temperature limiter Safety Thermostat Safety thermostat (overheat) Safety thermostat activated Safety thermostat activation Safety thermostat intervention Safety thermostat lock out Safety thermostat lockout Safety Thermostat neon Safety thermostat trips SE Second orange light Section A Section B Section C Section C Fault Section D Section D Fault Section E Section F Section G Section H Section I Section J Section J (Neon Flashing) Section J Fault Section K Section L Section M Section M (Neon Flashing) Sensor Sensor Fault Sensor Fault (Central Heating) Sensor Fault (Flow or Return) Sensor Fault (Hot Water) Sensor Fault Neon Sensor Fault Neons Sensor Flow SENSOR STUCK LOCKOUT Sequence Error SEr SERVICE SERVICE DUE Service Required SERVO MOTOR BLOCKED SET SF SH Short Cycling Shorted signal sHr Significant loss in pressure Simultaneous 1 Slow / 1 Fast SL Slow flash Slow flash (unspecified rate) Slow flashes Slow Flashing (2Hz) Slow flashing reset button SMELL OF COMBUSTION PRODUCTS Software Error SOOT FORMED Spare PCB Not Set Spark at ignition electrodes Spark does not stop Spark generator fault SR Stand-by STANDBY STANDBY NEON StBY Steady blue Steady light Steady on (Burner lit) STOP Summer mode LED SUMP FAN FAILURE THERMOSTAT SUP SWITCHED LIVE Switched Live 'On' Sy System pressure below 0.4 bar

U (22 codes)

U 00 U 1.2 U2-01 U4-65 U4-66 U4-67 U60 U60 °C U2453 UA-64 UA-65 UA-66 UA-67 UF Ultracom₂ 35 Store UNSTABLE FLAMES uP UU/1 UU/2 UU/5 UU/FF UU/tt

V (17 codes)

V/J VA VA-TS VALVE FEED BACK ERROR Venting VF Viessmann boilers Vitocrossal 200 Vitocrossal 300 Vitodens 100-W Vitodens 200 Vitodens 200-W Vitodens 222-F Vitotronic 050/200-H Vitotronic 200 / 300 Vitotronic 300 Volatile lockout

W (18 codes)

WAIT BOILER THERMOSTAT WAIT PELLET THERMOSTAT WATER AT REQUIRED TEMPERATURE Water Circulation LOCKOUT Water level control: lock out WATER OVERHEAT THERMOSTAT Water pressure WATER PRESSURE SENSOR WATER PRESSURE TOO HIGH WATER TEMPERATURE WATER TEMPERATURE LOW Water temperature too cool Water temperature too hot White reset neon illuminated Wiring fault Wiring Harness Wrench symbol Wrench symbol flashing

X (3 codes)

x[[ X00 Xtramax HE Range

Y (14 codes)

Yellow | On every 0.5 second Yellow | On permanently yellow ❍ YELLOW FLAMES YELLOW FLAMES SOOT FORMED YELLOW FLUE CONTROL LED Yellow L.E.D. E Yellow L.E.D. H Yellow L.E.D. H illuminated YELLOW LED BLINKS YELLOW LED LIGHT YELLOW LED ON every 0.5-secs Yellow LED On, Red LED On YELLOW LED Solid

Z (1 codes)

Zigbee Red (flashing)

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026