Icon
Reliable Heating and Cooling Solutions – Quality Service, Fair Prices, Guaranteed Satisfaction!

Follow Us On:

Logo
Contact US!

Rinnai RX199i Error Codes

Updated · by Aurora Star Tech Inc.

Rinnai RX199i error codes and diagnostic codes (also listed as REU-NB3237FF-US). The RX199i is a Rinnai tankless water heater in the SENSEI RX/CX series.

Homeowner with a tankless water heater problem? Call (647) 657-2977 or book a service call — licensed technicians across Vaughan and the GTA.

Rinnai RX199i error codes list

CodeMeaningSeverity
03Power interrupted during bath fillLow
10Air supply or exhaust blocked / condensate trap fullCritical
11No ignitionHigh
12Flame failureHigh
14Thermal fuse or overheat sensor trippedCritical
15Venturi control faultHigh
16Outlet water over-temperature safety shutdownCritical
17Venturi blockageHigh
18Gas valve air/fuel adjustment limit reachedHigh
19Electrical grounding / DC circuit shortHigh
21PC board data transfer errorHigh
22Gas valve adjustment faultMedium
25Condensate pump failure or clogged drainMedium
32Outlet water temperature thermistor faultMedium
33Heat exchanger thermistor faultMedium
34Combustion air thermistor (Non-SENSEI) / Lime detecting thermistor (RX/CX)Medium
38Exhaust gas temperature sensor (CO sensor on RH180)Critical
41Freeze protection / outdoor air temperature sensor faultMedium
51Inlet water temperature thermistor faultMedium
52Gas valve / modulating solenoid valve (POV) signal faultHigh
54High exhaust gas temperatureCritical
60Descaling countdown (minutes left)Low
61Combustion fan motor faultHigh
63Recirculation low flowMedium
65Water flow control device (servo) faultMedium
66Bypass flow servo faultMedium
70PC board faultHigh
71Gas solenoid valve fault (SV0–SV4 on Non-SENSEI)High
72Flame rod faultHigh
888Initial settings savedLow
AVenturi reset sequence: step A (RX/CX)Low
AdJVenturi reset sequence: step AdJ (RX/CX)Low
Bluetooth LED blinkingBluetooth LED blinking (push-button pairing mode)Low
Bluetooth LED solidBluetooth LED solid blue (app pairing mode)Low
dESDescaling (flush) modeLow
Diag historyMaintenance code history viewer (last 9 codes)Low
Diagnostic historyShow last 9 maintenance codesLow
EVenturi reset sequence: step E (code 17 or 52 only)Low
ECLReset completeLow
EndDescaling procedure endedLow
FVenturi reset sequence: step FLow
FFMaintenance performed (history marker)Low
InInitial setting: indoor installationLow
In Use fast flashIn Use light rapid flashLow
In Use slow flashIn Use light slow flashLow
In Use solidIn Use light steadyLow
LCScale build-up in heat exchanger (LC, LC0–LC9, 00)Medium
Lock keyController locked (key symbol)Low
LPGInitial setting: propane (LPG)Low
MuteController key beeps on/offLow
nGInitial setting: natural gasLow
OutInitial setting: outdoor installationLow
Parameter modeParameter settings menuLow
Parameter settingsParameter (installer settings) modeLow
Perf dataPerformance data viewer (live readings and counters)Low
Performance dataPerformance data readout modeLow
Priority lightPriority light on (this controller is in charge)Low
rnSDescaling finished, rinse nowLow
SECascade diagnostic display (error on secondary unit)Medium
SEtInitial settings not yet confirmedLow
SSService Soon alert (also listed as 55)Low
tVenturi reset sequence: step tLow
°C/°FTemperature scale switch (Celsius / Fahrenheit)Low

Troubleshooting the RX199i

Rinnai RX199i specs and setup data

All Rinnai Tankless Water Heater error codes →

Homeowner help: Tankless Water Heater No Hot Water: What to Check

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.

© 2026 Aurora Star Tech Inc. All rights reserved. This page may not be copied, republished or used to train other systems without written permission.

Emergency HVAC Service

647-657-2977