P0496: EVAP Flow During A Non-Purge Condition

What is P0496?

DTC P0496 (Diagnostic Trouble Code P0496) is defined as “EVAP Flow During A Non Purge Condition.”

It essentially means there’s an issue with the purge flow in the Evaporative Emission Control (EVAP) System, or the system is purging fuel vapor when it shouldn’t. 

The EVAP system seals the fuel system of the vehicle, helping prevent fuel vapor from escaping the fuel tank and being released into the atmosphere. Fuel vapor contains hydrocarbons that form smog when they react with sunlight and air, polluting the environment. 

The fuel vapor is contained in the EVAP canister. When the EVAP canister purge valve opens, the fuel vapor is siphoned by the vacuum of the intake manifold into the engine for combustion. In this way, the EVAP system also helps improve fuel efficiency. 

If the Engine Control Module (ECM) identifies an unplanned vacuum in the EVAP system’s intake vacuum flow, it will also store the P0496 code and turn on the Check Engine Light.

Normally, a planned vacuum would help the fuel (gasoline) reach the combustion chamber. But an unplanned vacuum or loose gas cap could lead to a vapor leak instead.

Note: In Asian vehicle brands, like Honda, Mazda, or Hyundai, this code may come up as “EVAP System High Purge flow” for the same issue.

Common symptoms

Code P0496 is hard to identify since there aren’t many obvious signs. 

But here are some symptoms that you could look out for:

• Engine Issues: The buildup of fuel vapor in the engine could cause problems with starting the vehicle. You may also notice rough idling or other performance problems with a P0496 EVAP flow issue.
• High Fuel Consumption: Due to an issue with the EVAP flow control, your engine may receive an improper air-fuel ratio, which affects mileage. You may also notice faster fuel depletion due to the evaporation of fuel.
• Catalytic Converter Damage: The engine running rich will lead to excess and incomplete fuel combustion. This unburned fuel is often ignited later in the exhaust system, where it burns, damages, or clogs the catalytic converter.
• Illuminated Check Engine Light: A blinking check engine light is the most noticeable indicator of a P0496 code since the issue has no obvious symptom that’s specific to this code.

Can I still drive?

Yes, you can still drive with a DTC P0496. But do ensure you get your vehicle checked as soon as possible.

Prolonged driving with an EVAP flow issue can lead to:

• Catalytic converter damage
• Engine damage
• Low fuel economy
• Increased fuel wastage
• Higher vehicle emissions

Note: Any Check Engine Light issue should be resolved as soon as possible, even if it’s a low-priority one like a code P0496. This way, you won’t ignore any major engine issues that could also trigger the Check Engine Light.

P0496 causes

The EVAP system consists of several components, including:

• Fuel tank (Gas tank)
• Fuel cap (gas cap)
• Charcoal canister (also known as the EVAP canister or vapor canister)
• EVAP vent valve (vent valve or solenoid valve)
• EVAP purge valve (purge valve or purge valve solenoid)
• EVAP hose (vacuum line)

As a result, several malfunctioning components can trigger code P0496. 

These include:

• Faulty EVAP purge volume control valve (EVAP purge valve, vapor canister purge valve, or canister purge solenoid) leading to a high purge flow
• Failed EVAP pressure sensor (fuel tank pressure sensor)
• Leaking EVAP system hose
• Faulty purge flow or EVAP system flow sensor
• Leaking or blocked EVAP canister
• Untightened or damaged fuel cap (gas cap)
• Faulty electrical connector or weak connections
• Short circuit in the sensor wiring

Diagnosis

Since the EVAP system is one of the most complex systems in your vehicle, a high purge flow problem isn’t easy to DIY. 

So, here’s how a mechanic would diagnose the issue:

1. Scan the engine light code and reset it. The mechanic will then run the vehicle and re-scan the code to verify the issue.
2. Check if the fuel cap is tightened properly.
3. Check for an engine vacuum leak.
4. Test the EVAP purge valve for vacuum issues or leakages.
5. Inspect the vent solenoid valve to see if it’s functional.
6. Check every valve in the EVAP system for blockages or debris.
7. Check the wiring and electrical connector in the EVAP system.
8. Test the fuel pressure sensor to see if the fuel tank pressure is within the optimal range specified in the manufacturer’s manual.

Possible repairs for P0496 & Costs

A mechanic would fix a code P0496 by:

1. Tightening or replacing the gas cap if it’s loose or damaged.
2. Repairing or replacing the canister purge solenoid (purge valve/purge solenoid valve) if there’s an engine vacuum leak.
3. Repairing leaks in the vent valve.
4. Replacing the electrical connector or repairing the EVAP pressure sensor signal wiring.
5. Replacing the fuel tank pressure sensor if it’s malfunctioning.
6. Repairing or replacing the vapor canister if damaged or faulty.

Once these repairs are done, the mechanic will re-scan the code and check if the vehicle still has a flashing Check Engine Light. 

Repair Costs:

Depending on their labor rate, a mechanic could charge between $75-$150 for a diagnosis. They’ll then be able to give you an approximate cost of repairs.

Here are estimated figures for repairing some EVAP system parts, including the cost of the parts and labor:

• EVAP Purge Volume Control Valve (Purge Valve): $150-$200
• EVAP Pressure Sensor (Fuel Pressure Sensor): $280-$330
• EVAP Line (Vacuum Line): $20-$100
• Canister Purge Solenoid: $150-$300