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P0496 Code: What Does EVAP System High Purge Flow Mean And How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

EVAP Flow During a Non-Purge Condition

Meaning

P0496 is a generic OBD-II code, but it seems to crop up frequently in vehicles made by GM. When a vehicle stores this trouble code, it means there’s an unidentified problem in the purge flow of the vehicle’s evaporation exhaust system.

If you’re working on a Mazda, Kia, Hyundai, Honda or Acura, the code reads with the same number and a slightly different description: EVAP System High Purge Flow.

Fortunately, the difference is purely semantic, and the troubleshooting process is nearly identical.

Causes

To make a long story short, there are only a few potential causes for code P0496.

  • Fault in the purge or vent solenoid/valve
  • Blockage in the EVAP canister
  • Faulty EVAP/fuel pressure sensor
  • Frayed, broken or loose wiring
  • Defective or broken canister purge valve
  • Broken/defective/failed vent solenoid

Symptoms

Here are the common symptoms of a P0496 OBD-II code most owners experience: first the Check Engine Light comes on. Next, there may be issues getting the vehicle to start. Finally, the engine may start “running rich”, causing issues with the catalytic converter and other components in the exhaust system.

You will notice issues with the check engine light and starting the car right away, but if the problem escalates to the third stage it will be difficult to ignore.

Diagnosis

Now that we understand the probable causes and symptoms, let’s talk about the troubleshooting process.

  • Most mechanics start by using an OBD-II scanner to pull any stored trouble codes in the system.
  • Pulling a P0496 code means the vehicle may have a problem with the EVAP system flow during a non purge condition. At this point the mechanic will clear all codes and re-scan the system with the vehicle running. This ensures the code wasn’t stored by mistake or registered as a one-off error code. If the code recurs, repairs are needed.
  • At this point, a mechanic will check all wiring and connectors in the EVAP flow system for fraying or damage.
  • Next, they will inspect the solenoids, valves and connectors to make sure they are intact.
  • Finally, the mechanic will check all valves in the EVAP system for blockage or debris that could be impeding their function.

Common mistakes

When troubleshooting a code P0496, some mechanics mistakenly assume the root cause lies in the evaporative emission control system or fuel pressure sensor. 

Due to this flawed perspective, many mechanics will actually replace entire components when the real issue is a simple vacuum leak. Cracked hoses get missed or the gas cap isn’t tightened down all the way, and the vehicle’s computer stores a code P0496.

Always start small and check for simple solutions before you start spending time and money swapping out major components.

How serious is this?

Unless the underlying problem causing code P0496 has advanced to the point it’s interfering with starting or normal operation, you probably won’t even notice it even when the engine light is on. 

It’s still important to find and fix the issue as soon as possible, though. An ounce of prevention is worth a pound of cure.

What repairs can fix the code?

These are the repairs that generally fix the issues causing a P0496 trouble code:

  • Scan and reset the vehicle trouble codes to ensure it’s not just a one time issue.
  • Verify the fuel cap is tightened down and seals properly
  • Check the purge solenoid valve, which may need replacement depending on the age of the part and the vehicle
  • Repair or replace the fuel tank pressure sensor and wiring

Related codes

None listed.

Conclusion

As with many issues, fixing code P0496 is yet another story of preventing minor problems from becoming serious problems. The longer the issue goes unaddressed, the more likely it is you will end up with an expensive and time-consuming repair.

If your check engine light is on but you can’t seem to determine any problems for yourself, take your vehicle into a shop and have it checked out by professionals immediately. You may end up with a quick and inexpensive fix that saves you the cost of major repairs later.