4 flashes = High-temperature lockout. ECO tripped at ~180°F tank shell temperature. Same as State 4-flash diagnostics.
Diagnostic sequence
1. Verify the lockout
Wait 30 minutes for tank to cool. Attempt reset. If trips again immediately, active fault.
2. Stuck thermostat
Main thermostat (integrated into gas valve) stuck closed. Burner over-fires; ECO trips. Dealer replacement.
3. Heavy sediment
Insulates temperature sensor. Flush tank.
4. Low water level
If not fully refilled after maintenance, partial water over-heats. Verify tank is full.
5. Power vent fan failure
If fan stops mid-cycle, exhaust backs up, temperature spikes.
Reset
- Wait 30 minutes for cooling
- Gas knob to "Off"
- Press red ECO reset button on gas valve
- Cycle gas valve and relight pilot
- Monitor LED
If 4 flashes returns repeatedly
Stop resetting. Call Whirlpool support or authorized installer.
Bottom line
Safety trip — investigate before repeated resets. Most common: stuck thermostat or heavy scale.