E05
State
Inlet Temperature Sensor (Thermistor) Fault
State tankless water heater displays E05 and will not run; occurs immediately when a hot water tap is opened.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Open or shorted inlet thermistor, Damaged sensor wiring harness, Faulty control board sensor input
How to Fix / Troubleshooting
Safety: Disconnect power before accessing wiring.
- Locate inlet thermistor: Remove the front cover. Find the thermistor mounted on or near the cold water inlet pipe.
- Inspect wiring: Check the sensor leads for cuts, burns, or loose connectors. Reseat the plug on the control board.
- Test sensor: With power off, disconnect the thermistor and measure resistance with a multimeter. Compare to the temperature/resistance chart in the State service manual. If readings are far off, replace the thermistor.
- Control board: If a known-good thermistor still triggers E05, the control board may have a failed sensor circuit and should be replaced by a qualified technician.
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Repair Difficulty
Medium
3/5
Required Part
Inlet Temperature Sensor (Thermistor)
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