State Water Heater E23 Error Code — What It Means
E23 is not a widely documented fault code in available State (A. O. Smith brand) water heater service literature. State tankless and residential water heaters typically display codes related to ignition failure, flame loss, blocked venting, low gas pressure, restricted water flow, or scale buildup. Because State fault codes are model-specific and the same number can mean different things on different platforms, you must confirm your exact model and fuel type before interpreting E23. Check the nameplate on your unit and compare the displayed code against the troubleshooting chart in your installation or service manual.
If your unit is a tankless gas model, E23 may relate to combustion air supply, venting restriction, gas valve operation, or flame-sensing problems. If it is an electric or heat-pump model, the code could involve sensor or control board issues. Without manufacturer documentation defining E23 for your specific State model, any repair should start with the basics: verify venting and airflow, check gas or electrical supply, inspect inlet screens and flow sensors, and look for scale or debris on critical components.
Common Causes
- Blocked or restricted venting Combustion air intake or exhaust vent obstructions prevent proper flame operation and trigger ignition or flame-loss faults on tankless units.
- Low or interrupted gas supply Insufficient gas pressure or a closed manual shutoff valve stops ignition and causes lockout codes on gas-fired models.
- Restricted water flow Clogged inlet screens, closed isolation valves, or low system pressure prevent the unit from calling for heat or maintaining flame.
- Scale or carbon buildup on sensors Mineral deposits on flame rods or thermistors, or soot on burners, interfere with flame detection and heat regulation.
- Faulty control board or wiring Corroded connections, damaged control boards, or loose harnesses generate spurious fault codes that do not match actual operating conditions.
Step-by-Step Fix
- Record the exact model number from the data plate on the side or front of the water heater, along with the full fault code displayed, and look up the code in your model’s installation manual or service bulletin.
- Turn off power at the circuit breaker (electric models) or set the gas valve to OFF and wait five minutes (gas models) to safely clear the control and reset internal timers.
- Inspect venting and combustion air if you have a tankless or power-vented unit, checking that intake and exhaust terminations are clear of snow, leaves, or debris and that vent pipes are properly pitched and supported.
- Check gas supply and pressure by confirming the manual gas shutoff valve is fully open and that other gas appliances in the home are operating normally, which indicates adequate supply pressure.
- Remove and clean inlet filter screens at the cold-water inlet, flushing any sediment or debris, and verify that isolation valves on both inlet and outlet are fully open.
- Inspect flame sensor and burner assembly for soot, scale, or corrosion, gently cleaning with fine sandpaper or a soft brush if accessible, and check that all wire harness connections to the control board are seated and free of corrosion.
- Restore power or gas and call for hot water, observing the display for any returning fault code, and note whether ignition occurs and flame remains stable during the full heating cycle.
Parts Often Needed
| Part | Notes |
|---|---|
| Inlet filter screen or sediment strainer | Amazon | Match thread size and micron rating to your State model’s cold-water inlet. |
| Flame sensor or flame rod | Amazon | Order by State model number if cleaning does not restore reliable flame detection. |
| Control board or user interface | Amazon | Required if diagnostics confirm board fault; must match your exact State model and serial range. |
When to Call a Pro
Call a licensed plumber or water-heater technician if E23 persists after you have verified venting, gas supply, water flow, and sensor cleanliness. Because E23 is not defined in standard State literature, professional diagnostic tools and access to the manufacturer’s service network may be required to interpret the code correctly for your specific model. A technician can measure gas pressure, test control-board outputs, verify flame-sense current, and cross-reference your serial number with any unpublished service bulletins. If your unit is still under warranty, contact State customer support before replacing any parts to preserve coverage and obtain the correct part numbers for your serial range.