Nissan Titan P0449: Vent Valve Solenoid – Circuit Malfunction


A somewhat common problem with Nissan Titan is he Code P0449. This code refers to a number that is given to you when you connect it to an OBD2 scanner. P0449 refers to the evaporative emissions control system (EVAP). It often appears with, or is related to, other codes, such as P0420, P0446, and very often P0455.

P0449 is typically not an immediate threat to your Titan’s drivability. However, whenever the engine maintenance light comes on, it is good to get it fixed as soon as possible. Additionally, a really good scanner will help you identify whether the vent valve is working properly or not. Most shops have these scanners. There is a link towards the end of the page on exactly how to perform a quality diagnosis with a scan tool.

Nissan Titan P0449 Definition

P0449 Nissan Titan
P0449 is a universal OBDII fault code. This means that regardless of the make or model of the vehicle, the code will mean the same (Titan or not, as long as it was manufactured after 1996).

P0449 indicates that the valve or solenoid circuit that controls the evaporation system is not working properly. The EVAP system sends fuel vapor from the gas tank to the intake manifold, a charcoal canister, or directly into the air, depending on the vehicle model. When this system malfunctions, fuel vapor is not removed properly.

The vehicle’s ECM (Engine Control Module) has detected that there is a fault in the circuit that controls the breather that releases fuel vapor from the system. The engine maintenance warning light will then come on.

Nissan Titan P0449 OBDII Code Symptoms

P0449 OBDII Code Nissan Titan Diagnostic
The check engine light is often the only sign that the P0449 code has been triggered

The P0449 code is usually not accompanied by any noticeable symptoms, other than the gas smell and the service engine soon light. You may also notice a slight decrease in fuel consumption.

You should especially notice the smell of fuel around the tank or fuel filler tube area.

The EVAP system deals directly with fuel vapors. If these vapors escape from the system, you will often faintly smell them while driving the vehicle.

Causes of Titan error code P0449

There are many things that can cause the P0449 fault code to activate on your Nissan Titan. Here are the most common problems that will launch the code along with a great video about the entire process:

  • fuel cap– A bad fuel cap can cause the code to be thrown for sure. Often, you will receive a message that the fuel cap is off even though it is on. If you get that message, in addition to a P0449, it can save you a lot of time and money by replacing the gas cap and seeing if it goes away.
  • EVAP system hose– The hose that carries fuel vapor from the fuel tank to the intake manifold may begin to leak. This will cause code P0449. Look for a tear or hole in it. This is one of the most common problems that cause this code. The hole can be very difficult to find without a smoke test.
  • Steam tank purge valve– One of the most common causes of the P0449 code is the steam tank purge valve. It is very easy to replace. There are a few clips that you have to find and remove. Here’s how to test a purge valve (YouTube).
  • Fuse/wiring problems– If the wiring going to the valve is compromised, it will cause P0449.
  • fuel tank sending unit– It is possible that the gasket that joins the fuel sending unit to the fuel tank is damaged. This can reduce the reservoir pressure and release the code. This should not be the starting point.
  • fuel filler neck– There is often a gasket where the fuel filler neck connects to the gas tank. This gasket can dry out, especially on vehicles that spend their time in dry climates. When it dries out, the fuel tank can no longer maintain pressure, and may erroneously display P0449.

Diagnostic P0449 – Nissan Titan

A mechanic has a wide range of instruments at their disposal to diagnose the cause of P0449 in your Nissan Titan. Here are the most common things done to diagnose the code:

  • The mechanic will inspect the gas cap to make sure it can withstand the pressure. If you receive a warning that your gas cap is off, even when it is on, replacing it will most likely clear this code.
  • The mechanic usually checks for other fault codes. The more fault codes there are, the easier it is to diagnose a problem. This is because when they appear together in certain combinations, there will often only be a few conditions that return any code combination at a time.
  • After finding out what fault codes appear with P0449, the mechanic usually inspects the EVAP system. This includes the purge valve, line, and reservoir.
  • The fuel tank pressure will be checked and controlled.
  • After the above checks and fixes, the mechanic will perform two tests: A smoke test, and they will use a scan tool to confirm that the EVAP solenoids and valves are working properly.

Are you still having problems? Here’s a super technical video that goes super in-depth about diagnosing P0449.

Most common fixes for P0449

P0449 Nissan Titan Code Fix

These are the most common Titan code P0449 fixes:

  • Replacing the gas cap
  • EVAP duct replacement
  • Replacing the vent valve
  • Wiring repair

Of all the items listed above, it would be wise to start with the gas cap and work your way up to the fuel tank, as the gas cap is by far the easiest and least expensive item to replace here.

Here is a great video on how to check the gas cap.

Good luck figuring out what’s causing your Nissan Titan to throw code P0449. We hope this helps you. If there is anything you think you could add, feel free to leave a comment below.

Is P0449 a serious problem?

Although P0449 is not going to cause the Titan’s engine to stop running, it should not be treated lightly. You could have a fuel leak. Pay close attention to the tank level and make sure there are no fuel leaks. We recommend that you take it in and/or take care of it immediately.


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