EVAP System High Purge Flow

The purge valve lets stored fuel vapors from the charcoal canister get pulled into the intake to be burned. It's supposed to be closed at idle and open at specific times when the engine can handle the extra fuel. P0496 sets when the PCM sees evidence of purge flow happening when the valve is commanded closed — like a sudden negative fuel trim shift at idle, or fuel tank pressure dropping unexpectedly. Almost always a purge solenoid stuck open mechanically.

Fuel trim or fuel tank pressure data indicates purge flow during a period when the purge valve is commanded fully closed.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 1Pinch off the purge line at the intake. If idle smooths out and trims clean up — purge valve is leaking through.
2. 2Bidirectional command the purge valve closed and verify zero flow with a vacuum gauge on the intake side.
3. 3Replace purge valve if it doesn't seal commanded closed.

• Purge valve stuck open (debris in solenoid, failed diaphragm)
• Cracked purge hose creating an unintended path
• Carbon-saturated charcoal canister leaking vapors
• Wiring fault holding purge solenoid energized

$80–$300.