P0496: EVAP System High Purge Flow
P0496 means the evaporative emission (EVAP) system detected fuel vapor flowing into the engine when the engine computer was not asking for it. It is usually a minor problem, most often a purge valve that leaks or sticks open, but it turns on the check engine light and can cause hard starting after refueling.
You can drive, but get it checked soon
The code does not trigger limp mode, so the car can normally be driven. Hard starting, a rough idle or a rich fuel mixture can get worse over time, and the car will not pass an emissions inspection while the light is on, so have it fixed soon.
What it means
The EVAP system catches fuel vapor from the tank in a charcoal canister. A purge valve lets the engine draw that vapor off at the right moments, and a vent valve opens the canister to fresh air. P0496 sets when vapor flows into the intake although the engine computer is not purging, which usually points to a purge valve that leaks or is stuck open. On GM and Saab vehicles, the system is sealed after a cold start with the engine running, and the code sets if tank vacuum stays above 2491 Pa for 5 seconds with the fuel level between 10 and 90 percent. The check engine light comes on after two trips. Ford replaced its older code P1450 with P0496, and Ford also sets it when vacuum is excessive during the leak test, for example with a vent valve stuck closed.
Likely causes
- Purge valve leaking or stuck openVery likely
Charcoal dust in the valve seat can keep it from closing fully, so vapor keeps flowing into the intake.
- Vent valve stuck closed, or vent filter or line blockedPossible
If the canister cannot draw in fresh air, the engine's suction builds excessive vacuum in the tank and the system sees too much flow.
- Vapor line kinked or blockedLess likely
A restricted line can upset the vacuum readings during the system's tests.
- Tank pressure sensor reading wrongLess likely
A faulty sensor can report excess vacuum that is not really there.
What you may notice
- Check engine light on
- Hard or long starting right after refueling
- Rough idle and a rich fuel mixture (the computer adds extra fuel)
- Hissing sound as vacuum releases when opening the fuel cap
What to check, cheapest first
- 1Open the fuel cap and listen for a hissing rush of air, which suggests vacuum is building in the tank. Make sure the cap is the correct type and seals properly. · you can do it
- 2Visually inspect the vapor lines and hoses near the canister and purge valve for kinks, cracks or pinching. · you can do it
- 3Check the vent filter and vent line for dirt, debris or blockage. · you can do it
- 4Read the stored codes and freeze-frame data, and check whether related codes such as P0497, P0441 or P0455 are also present. · mechanic
- 5Test the purge valve and vent valve for sticking or leaking, for instance by applying vacuum to the purge valve and checking that it holds when closed. · mechanic
- 6Check the tank pressure sensor reading against actual pressure, replace the faulty part, clear the code and complete a drive cycle to confirm the fix. · mechanic
Related codes
Frequently asked questions
Can I drive with P0496?+
Usually yes, since limp mode is not expected. Expect possible hard starting after refueling and a rough idle, and get it checked soon.
Can a gas cap cause P0496?+
It is not a typical cause. A loose cap tends to cause leak codes such as P0455. Still, confirm the cap is correct and seals, since it is a free check.
Will P0496 pass an emissions test?+
Not with the check engine light on. The code is emissions-related, so repair it, clear the code and complete a drive cycle before testing.
How hard is it to fix?+
Repair difficulty is rated easy, and a DIY fix is possible. Estimated labor is about 0.3 to 1.5 hours.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10