P0496 — Diagnose and fix
P0496 EVAP Flow During a Non-Purge Condition
The Evaporative Emissions System is designed to prevent fuel vapors from getting into the atmosphere during refueling. The system absorbs fuel vapors in a canister filled with activated charcoal while you fill the tank. After filling, the system opens a purge and vent valve. The engine sucks fuel vapor from the charcoal canister and burns it in the engine and the vent valve allows fresh air into the canister to purge it of all stored fuel vapor.
What the P0496 code means
Your vehicle knows when you’ve filled your tank because it monitors your fuel gauge. When is sees that fuel has been added to the tank, it performs the purge cycle. In the case of a P0496, the engine computer is sensing addition fuel vapor entering the engine when it’s not conducting a purge event. It knows this because it knows how much fuel it has added and it is seeing too little oxygen in the exhaust stream. So it concludes that the engine is getting fuel from the EVAP system.
What causes a P0496?
1) Faulty purge valve that’s stuck open along with a leak in an EVAP hose, faulty vent valve or faulty charcoal canister.
2) Faulty EVAP pressure sensor or fuel tank pressure sensor that’s allowing fuel vapor into the engine through the purge valve
What to check
Examine the purge valve for signs of charcoal particles. That would indicate a stuck open purge valve caused by a faulty charcoal canister that’s leaking charcoal particles into the purge line.
If you don’t find particles, use jumper wires to power and de-power the purge valve while it’s connected to a vacuum source (handheld vacuum pump) to see if it holds vacuum when closed.
If the purge valve leak when it’s in the close position,
If the purge valve checks out fine, perform the same checks on the vent valve and all the EVAP hoses.
©, 2022 Rick Muscoplat
Posted on by Rick Muscoplat