P0496: Evaporative Emission System High Purge Flow

What it means

The EVAP system detects purge flow when none is expected or more flow than commanded.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The EVAP purge valve meters fuel vapour from the charcoal canister into the engine to be burned. The control module compares expected purge with signals that indicate tank pressure or vapour flow; P0496 sets when flow is detected with purge off or is higher than commanded.

Common causes

Most likely first.

1. Purge valve stuck open
2. EVAP line cracked or disconnected

Symptoms

• Check engine light on
• Possible smell of fuel near tank or engine bay
• Failed emissions inspection
• Loose-cap warning may appear

How to diagnose it

1. Record freeze-frame data and check purge command and tank-pressure data to see when the unexpected flow occurred.
2. Inspect the purge valve, its hoses, and EVAP lines for a disconnected or cracked hose that could allow unmetered vapour flow.
3. With the engine off and the valve unpowered, check whether the purge valve seals as specified; flow through a valve that should be closed points to a stuck-open valve.
4. Use a scan tool to command purge and compare the response in tank-pressure or flow data with the manufacturer's expected response.
5. If the valve and hoses appear sound, test the EVAP system for leaks or abnormal flow using the vehicle manufacturer's procedure.

Common fixes

• Reconnect or replace a cracked purge hose or EVAP line.
• Replace a purge valve that does not seal when closed.
• Repair another confirmed EVAP leak or flow-path fault.

Can I keep driving?

Usually the vehicle remains drivable, but fuel vapour may cause a smell and the vehicle can fail an emissions inspection. Avoid ignoring a strong fuel smell, and have the system checked promptly if it persists.