Navien E002 Error Code — What It Means
The E002 error code on a Navien tankless water heater indicates low inlet water pressure or insufficient water supply. The unit has detected that it does not have enough water available to operate safely, so it shuts down to protect itself. This is an automatic-reset fault, meaning the error will clear on its own once normal water pressure and flow are restored to the heater.
Common Causes
- Closed or partially closed isolation valve The cold-water supply valve to the heater may not be fully open, restricting flow into the unit.
- Clogged inlet water filter or screen Sediment and debris in the inlet filter reduce water flow to the point where the unit cannot operate.
- Inadequate building water pressure The main water supply to your home may have low pressure or reduced flow.
- Restricted supply piping Kinks, blockages, or undersized pipes in the cold-water line feeding the heater limit flow.
- Faulty pressure sensor The sensor that monitors inlet pressure may be reading incorrectly even when supply conditions are normal.
Step-by-Step Fix
- Verify the cold-water isolation valve feeding the heater is turned fully open and that the main water supply to your home is on.
- Shut off power and water to the unit, then locate and remove the inlet water filter or screen assembly at the cold-water inlet connection.
- Inspect and clean the inlet filter under running water to remove sediment, mineral scale, or debris, then reinstall it.
- Check actual incoming water pressure at a nearby fixture or at the heater inlet to confirm your building supply meets the manufacturer’s minimum requirements.
- Restore power and water to the heater and open a hot tap to test operation and verify the E002 code clears.
- Inspect supply plumbing for kinks, restrictions, or undersized piping if the error persists despite good building pressure.
- Consider replacing the pressure sensor if all supply-side conditions are confirmed normal but the E002 fault continues to appear.
Parts Often Needed
| Part | Notes |
|---|---|
| Navien inlet water filter / screen | Amazon | Clean first, replace only if damaged or heavily scaled. |
| Navien pressure sensor | Amazon | Replace if the fault persists after verifying normal water supply conditions. |
When to Call a Pro
Call a licensed plumber or Navien service technician if the E002 error continues after you have confirmed the inlet valve is open, the filter is clean, and building water pressure is adequate. A pro can test the pressure sensor with proper diagnostic tools, inspect for hidden supply restrictions, and replace the sensor if needed. Also call for help if you are uncomfortable working with water or electrical connections on your heater or if your building’s water pressure is consistently too low and requires a booster pump or supply-line upgrade.