Navien Error Code E046: Outlet Thermistor Open/Short

How to Fix Navien Code E046

1. Step 1: Turn off power to the Navien unit at the wall switch or breaker. Wait 30 seconds, then turn it back on. If the error clears, it was a temporary glitch.
2. Step 2: Check that the unit's front panel is properly closed and all wire connections inside are snug. Do not remove the panel if you are not comfortable.
3. Step 3: If the error returns, call a Navien-qualified technician. They will need to test the thermistor resistance and likely replace it.

How to Reset Navien Code E046

1. Turn off the unit using the power button on the front panel.
2. Turn off the gas supply valve.
3. Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
4. Restore power at the breaker, then open the gas valve.
5. Turn the unit back on. If the error returns, the underlying issue needs repair.

Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.

What Does Navien Error Code E046 Mean?

The E046 code on your Navien unit means the outlet thermistor, a temperature sensor located on the hot water outlet pipe, is either open (infinite resistance) or shorted (near-zero resistance). This sensor tells the control board how hot the water leaving the heat exchanger is. When it fails, the board can't regulate the burner properly, so it shuts down the system to prevent overheating or damage. This is a common issue on Navien combi boilers and water heaters, especially after several years of use. For a homeowner, you'll likely see this error after the unit runs for a minute or two and then stops. The display will flash E046, and the unit will not heat water or run the central heating until it's fixed. The thermistor is a sensor mounted on the outlet pipe, often behind the front panel. While no gas or water leaks are associated with this code, you need a professional to replace the sensor to get your system back online. The fix requires removing the front cover, unclipping the sensor from the pipe, and installing a new one. Most homeowners should call a pro, but if you're handy, you can buy the right thermistor from a Navien supplier. Just be aware that mishandling the wiring can cause other issues.

Common Causes

• Thermistor sensor has failed due to age or thermal cycling fatigue
• Loose or corroded wire connection at the thermistor harness plug
• Damaged wiring between the thermistor and the main control board
• Control board failure that misreads the thermistor signal (rare)

Diagnostic Steps

Replacement Parts

Related Codes on Same Models

Other codes that affect the same Navien model families as E046.