ErrorCodePro · Appliance Error CodesA.O. Smith Tank Water Heater Error Codes: Full List & Meanings
Every A.O. Smith tank water heater error code we have verified against A.O. Smith's own support pages, with its official meaning. This list covers residential standard gas water heaters with honeywell gas control (flash code, 3-second pause). Codes vary by model, so confirm in your owner's manual. Support: A.O. Smith Residential Technical Assistance, 1-800-527-1953.
Smell gas? Leave the building now. Do not touch light switches, phones or appliances inside. Call your gas utility or 911 from outside. CO alarm sounding or headache, dizziness or nausea? Get everyone outside and call 911. Gas valves, burners, venting and wiring are for a licensed technician only. See our safety policy.
Codes by system
All A.O. Smith tank water heater error codes
Codes marked "Reset only" or "Service" have no separate page because the manufacturer publishes no owner fix beyond a reset or a service call.
| Code | Official meaning | System | Owner action |
|---|---|---|---|
| 0 flashes | Control off / pilot out; follow the lighting instructions on the water heater label. Service actions are for a qualified technician (A.O. Smith 1-800-527-1953). | Heating | Service |
| Solid | Pilot recently extinguished and thermopile cooling down; wait 10 minutes before relighting per the label. Service actions are for a qualified technician (A.O. Smith 1-800-527-1953). | Heating | Service |
| 1 flash | Normal operation (bright/dim heartbeat). | Status / reminder | Service |
| 2 flashes | Thermopile voltage low. Service actions are for a qualified technician (A.O. Smith 1-800-527-1953). | Heating | Service |
| 4 flashes | Temperature exceeded (ECO activated). Service actions are for a qualified technician (A.O. Smith 1-800-527-1953). | Heating | Service |
| 5 flashes | Sensor failure. Service actions are for a qualified technician (A.O. Smith 1-800-527-1953). | Sensors | Service |
| 7 flashes | Internal control failure. Service actions are for a qualified technician (A.O. Smith 1-800-527-1953). | Control / electronics | Service |
| 8 flashes | Power off failure (pilot present with knob off). Service actions are for a qualified technician (A.O. Smith 1-800-527-1953). | Control / electronics | Service |
Symptoms
Sources
Last reviewed: October 20, 2026. ErrorCodePro is not affiliated with A.O. Smith.