P0496 CODE: Evaporative (EVAP) Flow During a Non-Purge Condition

If you own a Mazda, Honda, Hyundai or Acura, you’ll notice that the description of this code is slightly different. With these models, it’s usually referred to as the EVAP system high purge flow but it refers to the same problem.

There are several ways in which the EVAP can malfunction. The EVAP is the system that ensures that fuel vapors don’t escape from your car’s fuel tank and into the atmosphere. It’s a sophisticated system that’s mainly comprised of fuel vapor pressure sensors, a vapor pipe, and a charcoal canister.

Another term you should familiarize yourself with is purge flow. This simply refers to the amount of fuel vapors that are channeled to the engine. This quantity varies depending on the amount of air that’s entering the system via the intake vacuum.

There’s an engine control unit, which is responsible for regulating the intake vacuum flow of the evaporative emission system. The charcoal canister, on the other hand, is the part responsible for storing fuel vapors from the fuel tank.

Under ideal conditions, the intake vacuum channels air to the charcoal canister. Once this air reaches the canister, the fuel vapors stored in the canister are expelled and sent to the engine. As they flow into the engine, the purge valves open, allowing the right amount of fuel vapors to flow through.

When the trouble code P0496 appears on your engine control module, it means that the intake vacuum flow is unusually high. Simply put; it means that there’s more air going into the charcoal canister, triggering an increase in the amount of fuel vapor being channeled to the engine. This process is what causes a high purge flow.

Causes of P0496 Code

There are a number of things that cause this code to appear such as:

• Plugged EVAP canister
• Blocked vapor canister
• Malfunctioning EVAP or fuel pressure sensor
• Poor electrical connection such as shorted wire (Hyundai, Isuzu)
• A faulty purge or vent solenoid/valve
• Defective purge flow sensor (Kia, Mazda)
• Leaking EVAP system hose (Hyundai)

Possible Solutions

The most effective solution for P0496 code is to look for a replacement for the purge solenoid valve. But, it’s important that you do proper diagnostics first before deciding to replace any element.

Ideally, you should have a scan tool that you can use to pinpoint where the exact problem is. When performing this test, the ignition should be on and the engine turned off. Next, close or seal the EVAP system using the seal/purge feature. As you do this, monitor the reading of the fuel tank pressure (FTP) sensor.

If the reading is much higher than the value set by the manufacturer, the best solution is to replace the solenoid valve. When purchasing the solenoid valve, ensure you buy one that’s specific to your car model.

If the purge valve turns out to be in good working condition, the other likely culprit of this problem is the FTP sensor. To check if this component is functioning properly, you’ll need a high-end scan tool that can monitor pressure once the fuel cap is removed. If the sensor indicates that there’s a vacuum yet the gas cap has been removed, then you’re certain that the FTP sensor is the source of the high purge flow.

Wrap Up

A P0496 code implies that there’s an unacceptable amount of intake vacuum flow into the evaporative emissions system. Some of the causes of this problem are: a faulty purge or vent solenoid, defective fuel pressure sensor, incorrect electrical connections and faulty vent solenoid. 

Though this trouble code doesn’t cause any major problems, it’s wise to address this issue as soon as possible. Over time, it can make it difficult to start the engine.