GMC Sierra P0449 Code Diagnosis: EVAP System

P0449 GMC Sierra

The most common issue is the GMC Sierra The Code P0449. The trouble code refers to a number you receive when your Sierra is connected to a computer. OBDII scanner. The evaporative emission control system is P0449. It is frequently found alongside, or closely related to, other codes such as P0420 and P0446.

P0449: Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction

Your Sierra is usually safe from P0449. Certainly anytime the service engine soon light is on, it’s good to deal with it as soon as possible though. You can also use a scanner to check if your valve is working correctly. They are common in shops. There’s a link towards the bottom the page on exactly how to perform that procedure. Otherwise, the article should show you how you can solve your problem.


Índice de Contenido
  1. GMC Sierra P0449 Definition
  2. GMC Sierra P0449 OBDII Code Symptoms
  3. Sierra P0449 Trouble Code Causes
  4. P0449 Diagnostics- GMC Sierra
  5. Most common P0449 fixes
  6. Do you consider P0449 to be a serious concern?

GMC Sierra P0449 Definition

The universal OBDII code P0449 can be used to diagnose trouble codes. The code can be used to indicate the same things regardless of the make and model of the vehicle (Sierra or otherwise) as long it was produced after 1996.

The P0449 code indicates that the solenoid or valve that controls the evaporation systems isn't working properly. Depending on your vehicle's model, the EVAP cycle fuel vapor out of the tank into an intake manifold. This system can fail to properly deal with fuel vapor if it malfunctions.

ECM (Engine Control Modul) detected a fault within the circuit controlling the vent to release fuel vapor. The service engine will soon follow up on this.


GMC Sierra P0449 OBDII Code Symptoms

P0449 OBDII Code Diagnosis GMC Sierra
The only indication that P0449 has been activated is the soon-lit service engine.

A P0449 Code will not usually be associated with other noticeable symptoms. Smells like gas And the service engine soon light. It is possible to notice a slight dip in fuel economy.

Particular attention should be paid to the smell of fuel near the fuel tank or fuel filler tube.

The EVAP system is responsible for fuel vapors. If these vapors are leaking from the system, you’ll often smell them faintly while operating the vehicle.


Sierra P0449 Trouble Code Causes

Many things can trigger the P0449 code in your GMC Sierra. Below are the top problems that could trigger this code, along with an excellent video.

  • Fuel Cap– A bad fuel cap can cause the code to be thrown for sure. Often, you’ll get a message informing you that the fuel cap is off even when it is on. You may not get the message but a P0449. This will save you time and money.
  • EVAP Hose– The hose that carries the fuel vapor from the fuel tank to the intake manifold can begin to leak. The P0449 code will be generated. It should have a tear or a hole. This is the main problem that can cause the code.
  • Vapor Canister Purge Valve– One of the most common causes of the P0449 code is the vapor canister purge valve. It’s really easy to replace. You will need to locate and take out a few clips. Here’s How to test a purge valle (YouTube).
  • Trouble with Fuse/Wiring– If the wiring going to the valve has been compromise, it’ll lead to the P0449.
  • Fuel Tank Sending Unit– It is possible for the gasket that attaches the fuel sending unit to the gas tank to go bad. It can lower the tank pressure, which could throw out the code.
  • Fuel Filler Neck– There is often a gasket where the fuel filler neck connects with the gas tank. It is possible for this gasket to dry, particularly if vehicles spend a lot of time in dry environments. When it dries out, the fuel tank can’t hold pressure anymore, it may erroneously throw P0449.


P0449 Diagnostics- GMC Sierra

The mechanic can use a range of instruments to determine the cause of P0449 on your GMC Sierra. The most commonly used methods to diagnose this code are:

  • A mechanic will examine the gas cap and verify that it is able to withstand high pressure. If you are getting a warning that your gas cap is off, even when it’s on, replacing it will more than likely clear this code.
  • A mechanic will usually check for any additional trouble codes. It is easier to diagnose problems if there are more codes. That’s because when they appear together in certain combinations, there will often only be only a few conditions that will throw any combination of codes at one time.
  • Once the mechanic has determined the trouble codes associated with P0449, he or she will usually Take a look at the EVAP system. These include the line and purge valve.
  • Monitor and check the pressure in your fuel tank.
  • After for the checks and fixes listed above, the mechanic will perform two tests: A smoke test, and they’ll use a scan tool to confirm that the EVAP solenoids and valves are operating properly.

Are you still having problems? Here’s a Super technical video This is a great article on how to diagnose P0449.


Most common P0449 fixes

P0449 Code Fix GMC Sierra

Below are the top Sierra P0449 fix options:

  • Replacement of gas cap
  • Replacement for EVAP Line
  • Vent valve replacement
  • Wiring repair

You should start with the gas caps and move on to the fuel tanks. This is because the gas caps are the easiest to replace and the least costly.

Here’s a great video on How to check your gas cap.

It's a good idea to try and figure out why your GMC Sierra is throwing the code P0449. We trust this helped. Please feel free to add anything below.


Do you consider P0449 to be a serious concern?

While P0449 is not going to cause the Sierra’s engine to stop running, it should not be treated lightly. Fuel leaks could be a problem. You should pay extra attention to the level of your fuel tank and ensure that you're not leaking fuel. It is best to have it checked and/or dealt with immediately.


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