OBD-II Trouble Codes

P0496 Code: EVAP Flow During a Non-Purge Condition

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Is your vehicle recording a P0496 on your OBD-II scanner? This code, which is one of the many OBD-II codes that can trigger the Check Engine Light, may not present any driving issues and won’t affect the safety of your vehicle, but it can result in engine damage if left unchecked.

To learn more about what a P0496 means for your vehicle, read on.

mechanic using an obd scanner to check car engine
Code P0496 means that your car computer has detected that the EVAP system is purging out fuel vapor when it shouldn’t be.

What Does the P0496 Code Mean?

OBD-II code P0496 stands for EVAP Flow During a Non-Purge Condition. It is a generic powertrain code that affects a variety of vehicles with both an evaporative emission control (EVAP) system and onboard diagnostics. If you see P0496 on your scanner, it simply means that your car’s computer believes the EVAP system is purging out fuel vapor when it shouldn’t be.

What is an EVAP System?

Although EVAP systems in general date back to the 1970s, modern enhanced systems became standard equipment in 1996.

The EVAP system is responsible for inhibiting harmful fuel vapors from escaping into the atmosphere. A device, called a charcoal canister, stores the vapors. Then, when the vehicle is running and conditions are correct, a purge valve opens, thereby creating a vacuum that pulls the vapors into the engine.

Once inside the engine, the vapors are burned as part of the normal combustion process.

Your car’s primary computer, which is often referred to as the powertrain control module (PCM) manages the purge valve and many other aspects of the EVAP system.

a car's purge valve
A broken purge valve can trigger P0496.

Modern EVAP systems are considered “enhanced” because, unlike older designs, they can run an extensive system self-test (also known as a monitor).

Under certain conditions, the PCM will close the canister vent valve, effectively sealing off the entire system. The device then opens the purge valve and uses a fuel tank pressure (FTP) sensor to measure the amount of vacuum (negative pressure) in the system.

The PCM uses the self-test to check for system leaks and incorrect purge flow. If there is either excess vacuum or vacuum that’s present at the wrong time, the PCM may set code engine code P0496 and trigger the check engine light.

Although it can affect any vehicle regardless of make, code P0496 often happens to owners of GM vehicles (Chevrolet, Pontiac, and Dodge, among others).

In Asian car models, such as Honda, Hyundai, or Mazda, this code may stand for “EVAP system high purge flow,” which means the same thing.

What are the Possible Causes of the P0496 Code?

Code P0496 is often set by a failed purge valve/solenoid that’s stuck open. Unfortunately, there are many other reasons the code may set. That’s why it’s a good idea to perform a thorough diagnosis before replacing any parts.

For proper diagnosis, you may consult a certified mechanic. But if you’re confident in your know-how on EVAP systems, here’s a list of all the potential causes of a P0496 code:

What are the Common Symptoms of the P0496 Code?

In some cases, an illuminated Check Engine Light may be the only symptom that accompanies a code P0496. Though other issues, such as rough running and other engine performance problems, may also result if fuel vapors are purged at the wrong time.

How to Diagnose the P0496 Code

Because there are many potential causes for code P0496, diagnosis can be extremely difficult. Here are a couple of videos to give you an idea of the troubleshooting process:

How to Fix the P0496 Code

As with most OBD-II trouble codes, you’re not going to find a “magic bullet” fix for a P0496. There are a variety of possible causes, as outlined above, which means there are different avenues of repair depending on what issue is causing the code to be stored.

You’ll need to diagnose the code accurately, as shown in the videos above, to find out the underlying cause and perform any necessary repairs.

And as we always say, all vehicles are different. When troubleshooting and repairing diagnostic trouble codes, make sure to consult the factory repair information for your application.

Repair manuals, such as those from Chilton, are useful, but an ALLDATA subscription is even better. ALLDATA has single-vehicle subscriptions for DIYers that provide detailed factory repair information.

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