TanklessCodes

Every tankless water heater error code

417 codes across 5 brands and 16 series, each one read off the manufacturer's own diagnostic manual for that exact series — because the same number does not mean the same thing on every generation.

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Rinnai error codes

Rinnai Non-SENSEI

Models: C199i (REU-KBD3237FFUDC-US), C199e (REU-KB3237WDC-US), RC80i (REU-KA2530FFUD-US), RC80e (REU-KA2530WD-US), RC98i (REU-KA3237FFUD-US), RC98e (REU-KA3237WD-US), RU80i (REU-KB2530FFUD-US), RU80e (REU-KB2530WD-US), RU90e (REU-KBD2934WD-US), RU98i (REU-KB3237FFUD-US), RU98e (REU-KB3237WD-US), RUC80i (REU-KBD2530FFUD-US), RUC90i (REU-KBD2934FFUD-US), RUC98i (REU-KBD3237FFUD-US), RUR98i (REU-KBP3237FFUD-US), RUR98e (REU-KBP3237WD-US), RUCS65i (REU-KCM2025FFU-US), RUCS75i (REU-KCM2528FFU-US), RUS65e (REU-KCM2025W-US), RUS75e (REU-KCM2528W-US), RE140i (REU-VE1720FFD-US), RE140e (REU-VE1720WD-US), RE160i (REU-VE2125FFD-US), RE160e (REU-VE2125WD-US), RE180i (REU-VE2432FFD-US), RE180e (REU-VE2432WD-US), RE199i (REU-VE2737FFD-US), RE199e (REU-VE2737WD-US), REP160i (REU-VEP2125FFD-US), REP160e (REU-VEP2125WD-US), REP199i (REU-VEP2730FFD-US), REP199e (REU-VEP2730WD-US), R50LSi (REU-VA2019FFUD), R63LSe2 (REU-VA2024WD(A)-UC), R75LSi (REU-VA2528FFUD(A)), R75LSe (REU-VA2528WD(A)-UC), R94LSi (REU-VA2535FFUD), R94LSe (REU-VA2535WD-UC), R98LSi (REU-VA3237FFU), R98LSe (REU-VA3237W-US), R98LSi-ASME (REU-VA3237FFU-ASME), R98LSe-ASME (REU-VA3237W-ASME), RL75i (REU-VB2528FFUD-US), RL75e (REU-VB2528WD-US), RL94i (REU-VB2735FFUD-US), RL94e (REU-VB2735WD-US), V53e (REU-VAM1620W-US), V53De (REU-AM1620WD-US), V65i (REU-VC2025FFU-US), V65e (REU-VC2025W-US), V75i (REU-VC2528FFU-US), V75e (REU-VC2528W-US), V94i (REU-VC2837FFU-US), V94Xi (REU-VC2737FFU-US), V94e (REU-VC2837W-US), RL75i (REU-VC2528FFUD-US), RL75i(A) (REU-VC2528FFUD-US(A)), RL75e (REU-VC2528WD-US), RL75e(A) (REU-VC2528WD-US(A)), RL94i (REU-VC2837FFUD-US), RLX94i (REU-VC2737FFUD-US), RL94e (REU-VC2837WD-US)

Code Error Verdict All series
02 No burner operation during freeze protection Call a pro Only series documented
03 Power interruption during bath fill DIY fix Compare 3 series
05 Bypass flow control device fault Part replacement Compare 3 series
10 Air supply or exhaust blockage Call a pro Compare 4 series
11 No ignition Call a pro Compare 4 series
12 Flame failure Call a pro Compare 4 series
14 Overheat switch or thermal fuse tripped Call a pro Compare 4 series
16 Outlet water temperature too high Call a pro Compare 4 series
19 Electrical grounding fault Call a pro Compare 3 series
25 Condensate pump fault or blocked condensate drain DIY fix Compare 3 series
31 Burner thermocouple out of range Call a pro Compare 2 series
32 Outgoing water temperature thermistor fault Part replacement Compare 4 series
33 Heat exchanger thermistor fault Part replacement Compare 3 series
34 Combustion air temperature thermistor fault Call a pro Compare 2 series
38 Exhaust gas temperature sensor fault Call a pro Compare 4 series
41 Freeze protection sensor fault Part replacement Compare 3 series
51 Inlet water temperature thermistor fault Part replacement Compare 3 series
52 Modulating solenoid valve (POV) signal fault Call a pro Compare 4 series
54 Exhaust gas temperature too high Call a pro Compare 3 series
57 Burner overheat bi-metal switch tripped Call a pro Only series documented
58 Secondary heat exchanger switch tripped Call a pro Only series documented
61 Combustion fan motor fault Call a pro Compare 4 series
63 Recirculation low flow DIY fix Compare 4 series
65 Water flow control valve fault Part replacement Compare 3 series
70 PC board fault Call a pro Compare 3 series
71 SV0-SV3 solenoid valve fault Call a pro Compare 4 series
72 Flame rod fault Call a pro Compare 4 series
73 Burner thermocouple fault Call a pro Compare 2 series
79 Water leakage detected Call a pro Only series documented
FF Maintenance performed marker DIY fix Compare 3 series
LC Scale build-up in the heat exchanger DIY fix Compare 2 series

Rinnai RH180 Hybrid

Models: RH180, REU-VA1320WF-US

Code Error Verdict All series
05 Air screen restricted DIY fix Compare 3 series
07 Circulation flow below 2.1 GPM DIY fix Only series documented
10 Air supply or exhaust blockage Call a pro Compare 4 series
11 No ignition Call a pro Compare 4 series
12 No flame Call a pro Compare 4 series
13 Combustion fault Call a pro Only series documented
14 Thermal fuse triggered Call a pro Compare 4 series
16 Over temperature warning Call a pro Compare 4 series
30 Flammable vapour sensor fault Call a pro Only series documented
31 Burner sensor fault Call a pro Compare 2 series
32 Heat exchanger outgoing temperature sensor fault Call a pro Compare 4 series
35 Tank temperature sensor fault Call a pro Only series documented
38 Carbon monoxide or flammable vapour sensor fault Call a pro Compare 4 series
52 Modulating solenoid valve signal fault Call a pro Compare 4 series
61 Combustion fan fault Call a pro Compare 4 series
63 Circulation flow below 1.3 GPM DIY fix Compare 4 series
71 Solenoid valve circuit fault Call a pro Compare 4 series
72 Flame sensing device fault Call a pro Compare 4 series
73 Burner sensor circuit fault Call a pro Compare 2 series
FE Flammable vapours detected Emergency — stop Only series documented

Rinnai SENSEI

Models: RU199i / RU199e (REU-N3237FF-US / REU-N3237W-US), RU180i / RU180e (REU-N2934FF-US / REU-N2934W-US), RU160i / RU160e (REU-N2530FF-US / REU-N2530W-US), RU130i / RU130e (REU-N2024FF-US / REU-N2024W-US), RUR199i / RUR199e (REU-NP3237FF-US / REU-NP3237W-US), RUR160i / RUR160e (REU-NP2530FF-US / REU-NP2530W-US), RSC199i / RSC199e (REU-NP3237FF-US(A) / REU-NP3237W-US(A)), RSC160i / RSC160e (REU-NP2530FF-US(A) / REU-NP2530W-US(A))

Code Error Verdict All series
03 Power interruption during bath fill DIY fix Compare 3 series
05 Bypass flow control device fault Part replacement Compare 3 series
10 Air supply or exhaust blocked, or the condensate trap is full Call a pro Compare 4 series
11 No ignition Call a pro Compare 4 series
12 Flame failure Call a pro Compare 4 series
14 Overheat sensor or thermal fuse tripped Call a pro Compare 4 series
15 Venturi control fault Call a pro Compare 2 series
16 Outlet water temperature too high Call a pro Compare 4 series
17 Venturi blockage Call a pro Compare 2 series
19 Electrical grounding fault Call a pro Compare 3 series
21 Data transfer error Call a pro Compare 2 series
25 Condensate pump fault or blocked condensate drain DIY fix Compare 3 series
32 Outgoing water temperature thermistor fault Part replacement Compare 4 series
33 Heat exchanger thermistor fault Part replacement Compare 3 series
38 Exhaust gas temperature sensor fault Call a pro Compare 4 series
41 Freeze protection sensor fault Part replacement Compare 3 series
51 Inlet water temperature thermistor fault Part replacement Compare 3 series
52 Gas valve fault Call a pro Compare 4 series
54 Exhaust gas temperature too high Call a pro Compare 3 series
61 Combustion fan motor fault Call a pro Compare 4 series
63 Recirculation low flow DIY fix Compare 4 series
65 Water flow control valve fault Part replacement Compare 3 series
70 PC board fault Call a pro Compare 3 series
71 Gas solenoid valve fault Call a pro Compare 4 series
72 Flame rod fault Call a pro Compare 4 series
FF Maintenance performed marker DIY fix Compare 3 series
SS Service soon reminder DIY fix Compare 2 series

Rinnai SENSEI RX

Models: RX199i (REU-NB3237FF-US), RX180i (REU-NB2934FF-US), RX160i (REU-NB2530FF-US), RX130i (REU-NB2024FF-US), RXP199i (REU-NBP3237FF-US), RXP160i (REU-NBP2530FF-US)

Code Error Verdict All series
03 Power interruption during bath fill DIY fix Compare 3 series
10 Air supply or exhaust blocked, or the condensate trap is full Call a pro Compare 4 series
11 No ignition Call a pro Compare 4 series
12 Flame failure Call a pro Compare 4 series
14 Overheat sensor or thermal fuse tripped Call a pro Compare 4 series
15 Venturi control fault Call a pro Compare 2 series
16 Outlet water temperature too high Call a pro Compare 4 series
17 Venturi blockage Call a pro Compare 2 series
18 Gas valve adjustment limit reached Call a pro Only series documented
19 Electrical grounding fault Call a pro Compare 3 series
21 Data transfer error Call a pro Compare 2 series
22 Gas valve adjustment fault Call a pro Only series documented
25 Condensate pump fault or blocked condensate drain DIY fix Compare 3 series
32 Outgoing water temperature thermistor fault Part replacement Compare 4 series
33 Heat exchanger thermistor fault Part replacement Compare 3 series
34 Lime detecting thermistor fault Part replacement Compare 2 series
38 Exhaust gas temperature sensor fault Call a pro Compare 4 series
41 Freeze protection sensor fault Part replacement Compare 3 series
51 Inlet water temperature thermistor fault Part replacement Compare 3 series
52 Gas valve fault Call a pro Compare 4 series
54 Exhaust gas temperature too high Call a pro Compare 3 series
61 Combustion fan motor fault Call a pro Compare 4 series
63 Recirculation low flow DIY fix Compare 4 series
65 Water flow control valve fault Part replacement Compare 3 series
66 Bypass flow servo fault Part replacement Only series documented
70 PC board fault Call a pro Compare 3 series
71 Gas solenoid valve fault Call a pro Compare 4 series
72 Flame rod fault Call a pro Compare 4 series
FF Maintenance performed marker DIY fix Compare 3 series
LC Scale build-up lockout DIY fix Compare 2 series
SS Service soon reminder DIY fix Compare 2 series

Rheem error codes

Rheem Tankless Gas

Code Error Verdict All series
1L Lime build-up in the heat exchanger DIY fix Only series documented
03 Communication failure between units or controls Call a pro Only series documented
05 Improper burner combustion (indoor units) Call a pro Only series documented
10 Vent blockage or insufficient ventilation Call a pro Only series documented
11 No flame detected Call a pro Only series documented
12 Flame lost after ignition Call a pro Only series documented
13 Poor combustion detected (indoor units) Call a pro Only series documented
14 Overheat limiter tripped Call a pro Only series documented
15 Water temperature reached 207°F Call a pro Only series documented
16 Outlet water above the set point Call a pro Only series documented
24 Remote control buttons held down DIY fix Only series documented
29 Condensate not draining, or heat exchanger too cold Call a pro Only series documented
31 Inlet thermistor malfunction Part replacement Only series documented
32 Heat exchanger thermistor malfunction Part replacement Only series documented
33 Outlet thermistor malfunction Part replacement Only series documented
34 Ambient thermistor malfunction Part replacement Only series documented
35 Thermistor connected incorrectly Call a pro Only series documented
51 Gas control valve: flame present after shutdown Call a pro Only series documented
52 PGFR (modulating gas valve) malfunction Call a pro Only series documented
61 Blower motor speed fault Call a pro Only series documented
65 Water volume control valve malfunction Part replacement Only series documented
66 Water by-pass valve malfunction Part replacement Only series documented
71 Gas control valve: inlet solenoid malfunction Call a pro Only series documented
72 Flame detected before ignition Call a pro Only series documented
76 Remote control communication fault Part replacement Only series documented
79 Blower motor current fault Call a pro Only series documented
80 Gas control valve: flame detected after shutdown Call a pro Only series documented
82 Control board program chip malfunction Call a pro Only series documented
90 Vent blockage detected before ignition Call a pro Only series documented
92 Neutralizer needs replacing (warning) Part replacement Only series documented
93 Neutralizer must be replaced (lockout) Part replacement Only series documented
99 Vent blockage detected after shutdown Call a pro Only series documented
P1 No hot water delivered DIY fix Only series documented

Noritz error codes

Noritz EZ Series & NCC199CDV

Models: EZ98DV (EZTR50), EZ111DV (EZTR75), NCC199CDV, GQ-C2859WX-FF US, GQ-C3259WX-FF US, GQ-C3259WZ-FF US

Code Error Verdict All series
10 Combustion fault recorded in history Call a pro Compare 4 series
11 Ignition failure Call a pro Compare 5 series
12 Flame rod does not detect flame Call a pro Compare 5 series
13 External carbon monoxide alarm triggered Emergency — stop Only series documented
15 Abnormally high input temperature Call a pro Only series documented
16 Abnormally high output temperature Call a pro Compare 5 series
20 Heat exchanger high limit switch triggered Call a pro Compare 5 series
21 Burner chamber high limit switch triggered Call a pro Compare 2 series
30 Air thermistor fault Part replacement Compare 4 series
31 Cold water thermistor fault Part replacement Compare 5 series
32 Hot water thermistor fault Part replacement Compare 5 series
33 Heat exchanger outlet thermistor fault Part replacement Compare 4 series
35 Exhaust thermistor fault Call a pro Compare 2 series
36 Heat exchanger inlet thermistor fault Part replacement Only series documented
61 Fan motor fault Call a pro Compare 5 series
65 Main water servo fault Part replacement Compare 3 series
66 Bypass water servo fault Part replacement Compare 3 series
70 Circuit board fault Part replacement Compare 5 series
71 Gas valve drive circuit fault Call a pro Compare 5 series
72 Flame rod circuit fault Call a pro Compare 5 series
73 Circuit board setting fault Call a pro Compare 5 series
76 Multi-system communication error Part replacement Compare 2 series
90 Combustion fault, unit shuts off Call a pro Compare 5 series
94 Exhaust temperature too high Call a pro Compare 2 series
760 Remote controller communication fault Part replacement Compare 5 series
C1 Service reminder DIY fix Compare 2 series

Noritz NCC199 & NRC111

Models: NCC199-SV, NCC199-DV, N-0841MC-DV, NRC111-SV, NRC111-DV, N-0842MC-DV

Code Error Verdict All series
10 Combustion fault, BTU drop Call a pro Compare 4 series
11 Ignition failure Call a pro Compare 5 series
12 Flame rod does not detect flame Call a pro Compare 5 series
14 Thermal fuse triggered Call a pro Compare 4 series
16 Abnormally high output temperature Call a pro Compare 5 series
20 High limit switch triggered Call a pro Compare 5 series
29 Neutralizer or water level electrode fault DIY fix Compare 2 series
30 Air inlet thermistor fault Part replacement Compare 4 series
31 Inlet thermistor fault Part replacement Compare 5 series
32 Outlet thermistor fault Part replacement Compare 5 series
33 Heat exchanger thermistor fault Part replacement Compare 4 series
59 Heat exchanger flow fault DIY fix Compare 3 series
61 Fan motor fault Call a pro Compare 5 series
65 Main flow control valve fault Part replacement Compare 3 series
66 Bypass flow control valve fault Part replacement Compare 3 series
70 Circuit board fault Part replacement Compare 5 series
71 Gas solenoid valve drive circuit fault Call a pro Compare 5 series
72 Flame rod circuit fault Call a pro Compare 5 series
73 Circuit board setting fault Call a pro Compare 5 series
90 Combustion fault Call a pro Compare 5 series
92 Neutralizer life cycle warning DIY fix Only series documented
93 Neutralizer life cycle has ended DIY fix Only series documented
99 Combustion fault, unit shuts off Call a pro Compare 4 series
760 Remote controller communication fault Part replacement Compare 5 series
F76 Multi-system communication error Part replacement Compare 2 series

Noritz NR50, NR66 & NR71

Models: NR50-OD, NR66-SV, NR66-OD, N-0531S-OD, NR71-SV, NR71-OD, N-0631S-OD

Code Error Verdict All series
10 Combustion fault, BTU drop Call a pro Compare 4 series
11 Ignition failure Call a pro Compare 5 series
12 Flame rod does not detect flame Call a pro Compare 5 series
14 Thermal fuse triggered Call a pro Compare 4 series
16 Abnormally high output temperature Call a pro Compare 5 series
20 High limit switch triggered Call a pro Compare 5 series
31 Inlet thermistor fault Part replacement Compare 5 series
32 Outlet thermistor fault Part replacement Compare 5 series
59 Heat exchanger flow fault DIY fix Compare 3 series
61 Fan motor fault Call a pro Compare 5 series
70 Circuit board fault Part replacement Compare 5 series
71 Gas solenoid valve drive circuit fault Call a pro Compare 5 series
72 Flame rod circuit fault Call a pro Compare 5 series
73 Circuit board setting fault Call a pro Compare 5 series
90 Combustion fault Call a pro Compare 5 series
99 Combustion fault, unit shuts off Call a pro Compare 4 series
760 Remote controller communication fault Part replacement Compare 5 series

Noritz NR98 & NR111

Models: NR98-SV, NR98-OD, NR98-DVC, NC199-OD, NC199-DVC, N-0751M-OD, N-0751M-DV, N-0751M-DVC, NR111-SV, NR111-OD, NR111-DV, NC250-SV-ASME, NC250-DV-ASME, N-0931M-OD, N-0931M-DV, NC380-SV-ASME, N-1321M-ASME

Code Error Verdict All series
10 Combustion fault, BTU drop Call a pro Compare 4 series
11 Ignition failure Call a pro Compare 5 series
12 Flame rod does not detect flame Call a pro Compare 5 series
14 Thermal fuse triggered Call a pro Compare 4 series
16 Abnormally high output temperature Call a pro Compare 5 series
20 High limit switch triggered Call a pro Compare 5 series
21 Pressure switch triggered Call a pro Compare 2 series
30 Air inlet thermistor fault Part replacement Compare 4 series
31 Inlet thermistor fault Part replacement Compare 5 series
32 Outlet thermistor fault Part replacement Compare 5 series
33 Heat exchanger thermistor fault Part replacement Compare 4 series
41 Flow sensor fault Part replacement Only series documented
56 Multi-system CCP valve fault Part replacement Only series documented
59 Heat exchanger flow fault DIY fix Compare 3 series
61 Fan motor fault Call a pro Compare 5 series
65 Main flow control valve fault Part replacement Compare 3 series
66 Bypass flow control valve fault Part replacement Compare 3 series
70 Circuit board fault Part replacement Compare 5 series
71 Gas solenoid valve drive circuit fault Call a pro Compare 5 series
72 Flame rod circuit fault Call a pro Compare 5 series
73 Circuit board setting fault Call a pro Compare 5 series
90 Combustion fault Call a pro Compare 5 series
99 Combustion fault, unit shuts off Call a pro Compare 4 series
760 Remote controller communication fault Part replacement Compare 5 series
F76 Multi-system communication error Part replacement Compare 2 series

Noritz NRC Series

Models: NRC661-DV, NRC661-OD, NRC711-DV, NRC711-OD, NRC663-FSV (EZTR40), NR501-OD, NR662-OD

Code Error Verdict All series
11 Ignition failure Call a pro Compare 5 series
12 Flame rod does not detect flame Call a pro Compare 5 series
14 Thermal fuse triggered Call a pro Compare 4 series
16 Abnormally high output temperature Call a pro Compare 5 series
20 High limit switch triggered Call a pro Compare 5 series
29 Condensate container clogged DIY fix Compare 2 series
30 Air thermistor fault Part replacement Compare 4 series
31 Cold water thermistor fault Part replacement Compare 5 series
32 Hot water thermistor fault Part replacement Compare 5 series
33 Heat exchanger thermistor fault Part replacement Compare 4 series
35 Exhaust thermistor fault Call a pro Compare 2 series
51 Gas solenoid valve failure Call a pro Only series documented
61 Fan motor fault Call a pro Compare 5 series
70 Circuit board fault Part replacement Compare 5 series
71 Gas solenoid valve drive circuit fault Call a pro Compare 5 series
72 Flame rod circuit fault Call a pro Compare 5 series
73 Circuit board setting fault Call a pro Compare 5 series
76 Display window communication fault Part replacement Compare 2 series
90 Air flow or combustion fault Call a pro Compare 5 series
91 Improper gas type Call a pro Only series documented
94 Exhaust temperature too high Call a pro Compare 2 series
99 Combustion fault, unit locked Call a pro Compare 4 series
760 Remote controller communication fault Part replacement Compare 5 series
C1 Scale build-up in the heat exchanger DIY fix Compare 2 series
CF Scale lockout Call a pro Only series documented

Noritz NRCP

Models: NRCP111-DV, NRCP98-DV

Code Error Verdict All series
Er11 Ignition failure Call a pro Compare 2 series
Er12 Flame loss Call a pro Compare 2 series
Er16 Overheating DIY fix Compare 2 series
Er20 Water high limit switch fault DIY fix Compare 2 series
Er29 Air pressure switch fault Call a pro Compare 2 series
Er31 Cold water thermistor open or short Part replacement Compare 2 series
Er32 Hot water thermistor open or short Part replacement Compare 2 series
Er33 Heat exchanger thermistor open or short Part replacement Compare 2 series
Er35 Exhaust thermistor open or short Call a pro Compare 2 series
Er38 Circuit board memory error Part replacement Compare 2 series
Er39 Flame detected after the gas valve closed Call a pro Compare 2 series
Er40 Gas leakage Emergency — stop Compare 2 series
Er41 Fan speed fault or exhaust blockage Call a pro Compare 2 series
Er43 Burner high limit switch fault Call a pro Compare 2 series
Er44 Possible pump failure Part replacement Compare 2 series
Er45 Water leak detected Call a pro Compare 2 series
Er46 Low recirculation flow DIY fix Only series documented
Er60 Hot water temperature abnormality Call a pro Compare 2 series
Er61 Fan RPM sensor fault Call a pro Compare 2 series
Er65 Water control valve fault Part replacement Compare 2 series
Er66 Water mixing valve fault Part replacement Compare 2 series
Er67 Gas modulation assembly fault Call a pro Compare 2 series
Er70 Circuit board fault Part replacement Compare 2 series
Er72 Flame detected before the gas valve opens Call a pro Compare 2 series
Er73 DIP switch setting fault Call a pro Compare 2 series
Er76 Control panel communication error Part replacement Compare 2 series
Er78 Quick Connect communication error Part replacement Compare 2 series
Er94 Exhaust overheating Call a pro Compare 2 series

Noritz NRCP Eco TOUGH

Models: NRCP1112-DV, NRCP982-DV

Code Error Verdict All series
Er11 Ignition failure Call a pro Compare 2 series
Er12 Flame loss Call a pro Compare 2 series
Er16 Overheating DIY fix Compare 2 series
Er20 High limit switch fault DIY fix Compare 2 series
Er29 Air pressure switch fault Call a pro Compare 2 series
Er31 Cold water thermistor open or short Part replacement Compare 2 series
Er32 Hot water thermistor open or short Part replacement Compare 2 series
Er33 Heat exchanger thermistor open or short Part replacement Compare 2 series
Er35 Exhaust thermistor open or short Call a pro Compare 2 series
Er38 Circuit board memory error Part replacement Compare 2 series
Er39 False flame detection Call a pro Compare 2 series
Er40 Gas leakage Emergency — stop Compare 2 series
Er41 Fan speed error Call a pro Compare 2 series
Er42 Loose jumper Part replacement Only series documented
Er43 Burner high limit switch fault Call a pro Compare 2 series
Er44 Recirculation abnormality DIY fix Compare 2 series
Er45 Water leak detected Call a pro Compare 2 series
Er60 Hot water temperature abnormality Call a pro Compare 2 series
Er61 Fan RPM sensor fault Call a pro Compare 2 series
Er65 Water adjustment valve fault Part replacement Compare 2 series
Er66 Mixing valve fault Part replacement Compare 2 series
Er67 Gas modulation assembly fault Call a pro Compare 2 series
Er70 Circuit board processor error Part replacement Compare 2 series
Er72 Flame detected before ignition Call a pro Compare 2 series
Er73 DIP switch setting fault Call a pro Compare 2 series
Er76 Display panel communication error Part replacement Compare 2 series
Er78 Quick Connect communication error Part replacement Compare 2 series
Er94 Exhaust overheating Call a pro Compare 2 series

Takagi error codes

Takagi Condensing

Code Error Verdict All series
031 Incorrect DIP switch settings Call a pro Compare 2 series
101 Abnormal combustion (warning) Call a pro Compare 2 series
111 Ignition failure Call a pro Compare 2 series
121 Flame loss Call a pro Compare 2 series
311 Output thermistor fault Part replacement Compare 2 series
321 Inlet thermistor fault Part replacement Compare 2 series
331 Mixing thermistor fault Part replacement Compare 2 series
341 Exhaust thermistor fault Call a pro Only series documented
391 Air-fuel ratio rod failure Call a pro Compare 2 series
441 Flow sensor fault Part replacement Compare 2 series
510 Main and solenoid gas valve fault Call a pro Compare 2 series
551 Solenoid valve fault Call a pro Only series documented
611 Fan motor fault Call a pro Compare 2 series
621 Exhaust fan motor fault (indoor models) Call a pro Only series documented
631 External pump fault Part replacement Only series documented
651 Flow adjustment valve fault Part replacement Compare 2 series
661 Water bypass valve fault Part replacement Only series documented
701 Proportional valve or computer board fault Call a pro Compare 2 series
711 Hi-limit switch or overheat cutoff fuse Call a pro Only series documented
721 False flame detection Call a pro Compare 2 series
741 Remote controller communication failure Part replacement Compare 2 series
761 Easy-Link communication failure Call a pro Compare 2 series
941 Abnormal exhaust temperature Call a pro Only series documented
991 Abnormal combustion Call a pro Compare 2 series

Takagi Non-Condensing

Models: T-D2, T-K4, T-KJr2

Code Error Verdict All series
031 Incorrect DIP switch settings Call a pro Compare 2 series
55 Abnormal solenoid gas valve (T-K4, T-KJr2) Call a pro Only series documented
101 Abnormal combustion (warning) Call a pro Compare 2 series
111 Ignition failure Call a pro Compare 2 series
121 Flame loss Call a pro Compare 2 series
311 Output thermistor fault Part replacement Compare 2 series
321 Inlet thermistor fault Part replacement Compare 2 series
331 Mixing thermistor fault (T-D2) Part replacement Compare 2 series
391 Air-fuel ratio rod failure Call a pro Compare 2 series
441 Flow sensor fault (Easy-Link systems) Part replacement Compare 2 series
510 Abnormal gas valves Call a pro Compare 2 series
611 Fan motor fault Call a pro Compare 2 series
651 Flow adjustment valve fault (Easy-Link systems) Part replacement Compare 2 series
701 Computer board fault Call a pro Compare 2 series
721 False flame detection Call a pro Compare 2 series
741 Remote controller communication failure Part replacement Compare 2 series
761 Easy-Link communication failure Call a pro Compare 2 series
991 Abnormal combustion Call a pro Compare 2 series

Using this table

Find your brand, then your series — not just your brand. A Rinnai code 34 is a different sensor on a SENSEI RX than on Rinnai's older units, and reading the wrong row costs money. If you are not sure which series you have, the model-number decoder matches the number on your rating label to the right table.

Every code page cites the document and page number it was transcribed from, so you can check it against the manufacturer yourself. Anything involving gas, ignition, venting or exhaust says the same thing every time: stop, and call a licensed professional.

This table is free to link to. If you help people with tankless units on a forum, tanklesscodes.com/error-codes is a stable, no-signup alternative to sending someone a 90-page PDF.