P0466

Universal

Evaporative Emission System Leak Detected (very small leak) / Purge Flow Sensor Circuit Range/Performance

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Low Severity

This code is associated with either a very small leak in the evaporative-emissions (EVAP) system or purge-flow sensor circuit performance outside the expected range. The EVAP system contains fuel vapors and routes them for controlled use by the engine; the vehicle monitors for leaks and checks purge-flow operation. The code alone does not identify which condition is present or prove that a particular part has failed. The check-engine light may be the only noticeable effect, though emissions performance or fuel-vapor containment may be affected.

Report an error with this code

⚠️ Before You Begin (Safety First)

This is generally not an immediate driving emergency if the vehicle runs normally and there is no fuel smell. If you notice a strong or persistent fuel odor, visible fuel leakage, or a change in how the vehicle runs, stop in a safe place and arrange an inspection. Keep ignition sources away from fuel vapors.

Common Symptoms

  • The check-engine light may be on, with no obvious change in driving.
  • A small EVAP leak may allow fuel vapor to escape and can sometimes cause a fuel-vapor odor.
  • A purge-flow sensor circuit performance issue may affect the vehicle's ability to monitor or control vapor purging; any drivability effects depend on the vehicle and fault.
  • An emissions inspection may be affected if the fault causes the system to fail its monitor.

Common Causes

  • A small leak in an EVAP hose, connection, seal, or other vapor-system component may trigger the leak-related interpretation.
  • A fuel-filler cap or its seal may not close or seal correctly, if applicable to the vehicle's system.
  • A purge-flow sensor, its wiring, or its electrical connections may produce an out-of-range or inconsistent signal.
  • A purge-control or vapor-flow problem elsewhere in the system may affect the monitored flow reading.
  • The code may need further testing to distinguish a leak condition from a purge-flow sensor circuit performance condition.

Diagnostic Steps

  1. With the vehicle parked safely and the engine off, check for a strong fuel odor or visible fuel leakage. If either is present, do not continue inspection; arrange professional help.
  2. Check that the fuel-filler cap, if fitted, is present and seated correctly. Inspect its seal for obvious damage, without assuming it is the cause.
  3. Look over accessible EVAP hoses and connectors for visible disconnection, cracking, or damage. Avoid disturbing parts that are difficult to reach.
  4. If a suitable scan tool is available, record the code and any related codes before clearing anything. Codes and scan data can help distinguish a leak investigation from a sensor-circuit investigation.
  5. If the code returns or the cause is not apparent, have the vehicle tested using model-specific procedures; leak testing and electrical diagnosis may require suitable equipment.

When to Call a Professional

A technician can review the stored code and related scan data, then determine whether leak testing or purge-flow sensor circuit diagnosis is appropriate for the vehicle. Depending on the design, useful checks may include a smoke test of the EVAP system and inspection of the sensor, connectors, wiring, and purge operation. Vehicle-specific service information is needed for test procedures and interpretation.

Compare component listings

Confirm diagnosis and vehicle fitment before buying. A listing does not prove that a part needs replacement. We may earn a commission from qualifying purchases.

Search Amazon Search eBay

Commonly Asked Questions

Does P0466 prove that there is an EVAP leak?

No. The definition associates the code with a very small EVAP leak or purge-flow sensor circuit range/performance. Further diagnosis is needed to determine which condition applies.

Does this code mean the purge-flow sensor must be replaced?

No. A sensor, wiring, connector, purge-flow issue, or an EVAP leak may be involved. Testing is needed before replacing parts.

Can I drive with this code?

If the vehicle runs normally and there is no fuel smell or visible leak, the code is generally not an immediate driving emergency. Stop and seek help if you notice strong fuel odor, leakage, or a significant change in vehicle operation.

What tests can distinguish the possible causes?

A technician may use EVAP leak testing, such as a smoke test where appropriate, and check purge-flow sensor data and its circuit. The correct procedure depends on the vehicle.

Browse Available Code Guides

Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.