Water Heater — Tankless error codes

116 codes from 13 manufacturers, each with its meaning and the document it comes from. Open a code for the details, or search every system.

Fogatti (13)

• E1Ignition failure - no ignition, or accidental flameout during operation
• E2False fire - a flame signal was detected BEFORE ignition (beeping alarm); clear the fault after a power-off
• E3Thermostat malfunction - temperature control failed during start-up or operation (can also be water…
• E4Inlet temperature probe fault - probe open or shorted
• E5Fan failure - no fan signal detected during start-up or operation
• ECWired Digital Controller mismatch - the wired Digital Controller does not match the water heater (a…
• 11Ignition failure (older-firmware display code; equivalent to E1)
• E0Outlet temperature probe fault - probe open or shorted
• E6Over-heating fault - water temperature exceeded 176 degF (80 degC) for 3+ seconds
• E7Gas valve fault - main valve opens or shorts / proportional valve fault (before or during combustion). On…
• E8Wind/air-pressure switch failure (IS7/IS8 Pro - mechanical pressure switch): switch closed when powered for 5…
• E9Proportional gas valve fault - the proportional valve is detected open during start-up or normal operation…
• EnWater heater timeout - continuous-use set timer reached

Furrion FWH09 (tankless) (12)

• E0Water-outlet temperature sensor fault. Control board cannot read outlet thermistor.
• E1Flame sense fault during ignition. Burner attempted to light but flame sensor did not detect combustion.
• E2Flame sensing interrupted during normal operation (buzzer sounds) — the control board lost the flame signal…
• E3Over-temperature mechanical sensor faulty. Manual high-limit (ECO) switch or thermistor reading over-limit.
• E4Water-inlet temperature sensor fault.
• E5Air pressure switch / blower circuit fault. Blower not running or pressure switch not closing.
• E6Temperature surge — output temperature swung outside expected range.
• E7Solenoid (gas) valve fault.
• E8Air pressure switch failure: switch not detected for 7 seconds before ignition, or cuts off for 2 seconds…
• E9Flame sensed before ignition (buzzer) — board detects flame current at the rod BEFORE commanding the gas…
• EnSystem timer error: water heater has operated continuously for longer than 20 minutes
• FdWater heater operating in Winter Use Mode (freeze protection active)

GE Profile PR60PTLWBU (13)

• E0Water outlet temperature sensor fault — damaged sensor or a broken/cut/shorted wire. Service required.
• E1Flame sense fault — burner did not ignite or flame not sensed. Causes: insufficient fuel supply (open all gas…
• E2Before ignition, a flame signal was detected (system fault). Service required.
• E3Thermal cutout fault (system fault). Flow hot water through a faucet continuously for 30 s, then restart; if…
• E4Water inlet temperature sensor fault — damaged sensor or a broken/cut/shorted wire. Service required.
• E5Air pressure switch or fan motor fault — exhaust blockage (clear the air outlet), high winds on the exhaust…
• E6Outlet temperature-limit protection — outlet water exceeded 65°C (149°F) for 3 consecutive seconds. Causes…
• E7Gas solenoid valve fault (system fault). Service required.
• E8Fan speed exceeds limit — fan speed exceeded its limit for 5 seconds. Check the altitude setting: 'LO' for…
• EnMax Time Limit — the water heater was in constant operation for over 40 minutes.
• EuUnder-voltage or over-voltage detected — supply voltage dropped below 9.5 VDC or rose above 19 VDC.
• E9Flame Freeze Prevention did not ignite — insufficient fuel supply for the freeze-prevention flame (open all…
• -0-CPU internal fault or A/D reference circuit fault — unit is locked; must cycle power

Girard GSWH-2 (12)

• E0Water outlet temperature probe (thermistor) failure — open or short circuit detected on the outlet thermistor…
• E1Ignition failure or flame-out during ignition trial — board made 2 attempts (3 trials total on older…
• E2Flame sensing interrupted during normal operation (buzzer sounds). Board saw flame at ignition, lost it…
• E3ECO (Emergency Cut Off / high-limit) thermostat opened — outlet water temperature exceeded 140°F (60°C)…
• E4Water inlet temperature probe (thermistor) failure — open or short circuit detected on the inlet thermistor…
• E5Blower motor failure — no motor signal detected by the control board before ignition or during normal…
• E6Over-temperature — outlet thermistor measured water temperature above 140°F (60°C) for 3 seconds
• E7Linear (modulating) gas valve failure — controller detects open circuit in linear valve control circuit…
• E8Air pressure switch fault — switch not detected closed for 7 seconds before ignition, or opened for 2 seconds…
• E9Flame sensor short — flame sensed BEFORE ignition attempt (buzzer sounds). Indicates short in the flame…
• EnSystem Timer — water heater ran continuously for 20 minutes. Safety timer to prevent unattended operation if…
• FdWinter Use Device (WUD) engaged — bimetallic thermostat on the hot water line turned ON at 38°F (3°C)…

RecPro RP-1057 (11)

• E0Hot water outlet temperature probe broken or short circuit
• E1Ignition failure, no ignition
• E2Flame signal detected BEFORE ignition (pseudo-flame), beeping alarm
• E3Thermostat malfunction detected during start-up or operation
• E4Hot water outlet temperature probe broken or short circuit
• E5No fan (blower) working signal detected during start-up or operation
• E6Over-temperature fault (water 140 F / 60 C or higher for 3 s+)
• E7Gas-valve solenoid broken or short circuit
• E8Fan motor speed exceeds preset
• E9Pseudo-fire fault - start-up ignition detected a flame signal (buzzer alarm)
• ENWater heater timer set to Open ('En' is set to open)

Suburban (1)

• LOCKOUTSuburban Nautilus IW60: Module board LOCKOUT - the water heater fails to ignite after three…

Suburban IW60 / Nautilus (10)

• E1Ignition fault - flame signals undetectable after igniting twice (LOCKED)
• E2Accidental stall fault - loss of flame during combustion (LOCKED)
• E3False fire / Residential fire fault - flame signals detected before start, or flame signal detected after…
• E4Water overheating - water output NTC > 90 C (194 F) (LOCKED)
• E5Thermal switch fault - HI limit (Auto Reset or Manual Reset) open (LOCKED)
• E6Air pressure switch fault - sail switch open OR fan abnormal (LOCKED)
• E7Water entry NTC fault - inlet NTC open or short circuit (AUTOMATIC RECOVERY)
• E8Module Board fault (LOCKED) - per IW60 troubleshooting guide, replace Module Board
• E9Water NTC fault — water input or output NTC open/short circuit (AUTOMATIC RECOVERY). Per service manual…
• ECCommunication failure - line controller communication failure (AUTOMATIC RECOVERY)

Suburban ST42A / ST60A (11)

• E0Outlet temperature probe fault — probe open or shorted
• E1Ignition failure — flame signal undetectable after three ignition attempts
• E2False Fire Fault / Residential Fire Fault — flame signals detected before ignition start, or residual flame…
• E3High limit fault — limit switch off
• E4Inlet temperature sensor fault — probe open or shorted
• E5Fan failure — no fan speed signal detected
• E6Over-temperature fault — outlet water too hot
• E7Gas valve wire fault — main gas valve wire opens or shorts unexpectedly
• ECCommunication Failure (LOCKED) - the line controller (User Control Panel) has lost communication with the…
• E8Pressure switch failure - pressure switch abnormally closed or disconnected
• EnWater heater timeout - unit ran continuously for longer than 20 minutes

Suburban ST42A / ST60A (recirc models) (1)

• E9Recirculation failure — pump will not prime due to air in recirculation line

Truma AquaGo (27)

• W1 (flash: 7s,1l)Flame not detected at burner after gas release and ignition (3 attempts, ~30 s apart)
• W2 (flash: 6s,1l,1s)Error at EOS (exhaust) or BOS (burner) over-temperature switch — open or unplugged
• W3 (flash: 6s,2l)Error at EPS (exhaust pressure switch) — either did not close when fan ran, or is closed when fan is off
• W4 (flash: 5s,1l,2s)WOS (water over-temperature switch) opened — water exceeded 185 °F (85 °C)
• W5 (flash: 5s,1l,1s,1l)Flame detected at incorrect time — before ignition, before gas release, or after gas switched off
• W6 (flash: 5s,2l,1s)Error in safety circuit for gas valve — heating request present but gas cannot be released because one of…
• W7 (flash: 5s,3l)Burner MCU internal RAM error — safety variables corrupted
• W9 (flash: 4s,1l,2s,1l)WOT (water outlet temp sensor) — short circuit, open, or unplugged
• W10 (flash: 4s,1l,1s,1l,1s)Safety circuit error — heating request present but valve-actuation signal not activated
• W11 (flash: 4s,1l,1s,2l)MCU watchdog did not release the gas path despite heating request
• W12 (flash: 4s,2l,2s)Internal error — generic controller fault
• W13 (flash: 4s,2l,1s,1l)Short-circuit detection in gas valve shut-off section — drew >1000 mA and shut off
• W16 (flash: 3s,1l,4s)Malfunction of the MCU — internal control unit error
• W20 (flash: 3s,1l,1s,1l,2s)WIT (water inlet temp sensor) — short, open, unplugged, OR sensing colder than 14 °F (-10 °C)
• W22 (flash: 3s,1l,1s,2l,1s)Gas valve modulation section — modulator coil shorted, open, or unplugged
• W23 (flash: 3s,1l,1s,3l)Supply voltage too high — detector measured >16.4 V
• W24 (flash: 3s,2l,3s)Supply voltage too low — detector measured <10 V
• W25 (flash: 3s,2l,2s,1l)Flue fan current out of limits — drawing more or less than permitted
• W28 (flash: 3s,3l,2s)Too low gas pressure — supply insufficient for demand
• W29 (flash: 3s,3l,1s,1l)Too high heat power required — demand exceeds appliance capacity
• W30 (flash: 3s,4l,1s)Risk of freezing — appliance internal temp below 27 °F (3 °C)
• W31 (flash: 3s,5l)Decalcification finished -- this is a STATUS code, not a fault. Confirms decalcification cycle ran to…
• E1Failed flame ignition after multiple attempts (2025 tech-tip refresh)
• W27Water circulation pump is running dry (flash S,S,S,L,L,S,L,L) - the circulation pump is not generating water…
• W29Too high heat power required (flash S,S,S,L,L,L,S,L) - occurs when hot water is used simultaneously at…
• W30Risk of freezing (flash S,S,S,L,L,L,L,S) - the temperature inside the AquaGo has dropped below 27 F (3 C).…
• W31Decalcification finished (flash S,S,S,L,L,L,L,L) - the AquaGo has completed a full decalcification cycle.…

Truma AquaGo (comfort plus) (1)

• W21 (flash: 3s,1l,1s,1l,1s,1l)WCT (circulation line temp sensor) — short, open, unplugged, OR colder than 14 °F (-10 °C)

Truma AquaGo (comfort/comfort plus) (2)

• W26 (flash: 3s,2l,1s,1l,1s)Circulation pump current out of limits
• W27 (flash: 3s,2l,1s,2l)Circulation pump running dry — no water flow detected. Pump retries 20 times at 30 s intervals; error clears…

Truma AquaGo (with antifreeze kit) (2)

• W32 (flash: 2s,1l,4s)Current too low in antifreeze kit — possible cable break
• W33 (flash: 2s,1l,4s,1l)Current too high in antifreeze kit — possible short circuit