P0499 – Evaporative emission system vent valve control circuit high

The P0449 OBD2 code indicates you have a malfunction in the vents of your evaporative emission control system. This leads to an increase in the number of smog-producing compounds in your exhaust.

Ultimately, the P0449 trouble code is often more of a problem for the environment than for your car. You’ll still want to repair it as quickly as possible to keep your vehicle operating at top efficiency. Read on below to find out how to diagnose and repair the P0449 code.

P0449 code definition

Evaporative emission control system vent valve/solenoid circuit malfunction

Here's where you can get a thorough understanding of the P0499 OBD2 code
If you want to learn about the P0499 OBD2 code, this is the right place

What does P0449 mean?

The P0449 OBD2 code relates to your evaporative emission control (EVAP) system. This system is designed to reduce the harmful emissions put out in your exhaust.

The fuel vapors your car runs on contain hydrocarbons, which form smog once they react with the outside air. The EVAP system passes these vapors through a charcoal canister. Potential pollutants are absorbed, and the cleaned carbon dioxide is sent back to the intake manifold for the car’s air/fuel mixture.

Two valves control the passage of vapors through the EVAP system. The vent control valve allows fuel vapors in. On the other side, the purge valve releases the carbon dioxide back into the engine.

If the P0449 trouble code activates, it’s telling you there’s a problem with the vent valve. This could mean the valve is stuck open, letting hydrocarbons escape freely into the atmosphere. Since your car can release pollutants even if it’s not running, this is a more serious concern for the environment than for your vehicle.

What are the symptoms of the P0449 code?

Likely, you won’t experience any drivability issues. The main symptoms of P0449 are:

  • Activation of the check engine light,
  • The smell of fuel around your car, even if it’s not running.

What are the causes of P0449?

  • The gas cap is missing or damaged,
  • EVAP hoses are damaged or leaking,
  • Damaged wiring around the valves,
  • The charcoal canister is damaged or leaking,
  • Vent valve or solenoid is damaged or faulty,
  • ECU or PCM is faulty.

How serious is the P0449 code?

The P0449 trouble code is of low severity in terms of your vehicle’s health. You can continue to drive your car worry-free while you diagnose and repair this code. However, this code will cause you to fail emissions tests, so you’ll need to repair it before your next inspection.

How to diagnose the P0449 code

Digital multimeter is the one of the equipment to diagnose the P0449 OBD2 code.
Digital multimeter is the one of the tools to diagnose the P0449 OBD2 code.

Tools you’ll need:

  1. Scan your vehicle for other trouble codes and fix any others that come up first. Also, read your freeze frame data to see what conditions were present when the code was set.
  2. Inspect your gas cap for damage and make sure it’s secured tightly.
  3. Check the hoses around the EVAP system for cracks and damage. Especially pay attention to those hoses connected to the engine air box.
  4. Visually inspect all the wires connected to the harness. Replace any with visible damage, and ensure none are shorted to each other or the ground.
  5. Use a digital volt ohmmeter to check for continuity in the wires to and from the PCM and ECU.
  6. Inspect both the charcoal canister and the fuel tank for damage. If you see a lot of build-ups, they may need to be cleaned.
  7. Use a digital multimeter to test the vent valve and solenoid. Make sure there is power running through both the positive and negative charges on the two-wire connector. If power runs through one but not the other, it could be a faulty wire or the solenoid itself.
  8. Check the resistance of the vent using a digital volt-ohm meter. With Chrysler, Dodge, and Jeep vehicles, this code is often caused by a faulty coil inside the vent valve. Compare your readings with the specifications in your manual, and replace the valve if it’s too low.
  9. Conduct a vacuum test on your EVAP system with a vacuum pump to ensure the valves are holding pressure.

Common mistakes to avoid while diagnosing the P0449 code

Many people instantly go to replacing the gas cap anytime there’s a trouble code related to the EVAP system. With this particular code, you want to make sure you check both the vent valve and solenoid as well. This is more likely to be the cause of P0449.

What should you do to fix the code P0449?

After every step of this repair, clear the codes and scan your car again. This will prevent you from making unnecessary repairs and help you narrow down the root cause of the issue.

  1. Replace any damaged hoses or wires found in your diagnosis. Ensure all replacements are securely connected.
  2. Replace the gas cap, even if there’s no visible damage. Deterioration of the gas cap can’t always be seen with the naked eye, and this cheap repair can often clear EVAP trouble codes. Make sure you use an OEM replacement. A misfitting gas cap can also trigger OBD2 codes.
  3. If your vent valve fails the vacuum test, remove it and clean it with a throttle body cleaner. Reinstall it and test it again. If it still fails, replace it.
  4. Replace the vent valve solenoid.
  5. If the code still has not cleared, you may have a more serious problem with your PCM. Take your car to a mechanic for further diagnosis.

The video about how to diagnose and fix P0449:

The way to fix the P0449 code

Tips to avoid P0449 in the future

Make sure you firmly reattach your gas cap after every fill-up. Small leaks in the fuel tank can trigger a host of EVAP system-related trouble codes, including P0449.

Corrosion and debris in your engine can cause damage to the wiring and hoses, another potential cause of P0449. Using a rust-preventing treatment on your engine can reduce corrosion. This extends your overall engine life as well as preventing many diagnostic trouble codes.