How serious is an EVAP system leak?

EVAP leaks are generally not dangerous to drive with but will cause a failed emissions test. Small leaks are less urgent, but large leaks should be repaired soon to prevent fuel vapor release.

How much does it cost to fix an EVAP leak?

Repairs range from $10 for a new gas cap to $200-$600 for purge valve, vent valve, or charcoal canister replacement. Smoke testing to locate the leak typically costs $50-$100.

P0459

Evaporative Emission Control System Purge Control Valve Circuit High

Moderateevaporative

Overview

The P0459 code indicates the PCM has detected a evaporative emission control system purge control valve circuit high condition in the evaporative emission control (EVAP) system. The EVAP system prevents fuel vapors from escaping into the atmosphere by routing them to the engine for combustion. A fault in this system can result in harmful fuel vapor emissions and a failed emissions test.

Symptoms

Difficulty fueling (pump keeps shutting off)
Gas cap warning light
Slight decrease in fuel economy
Check Engine Light (MIL) illuminated

Common Causes

Damaged charcoal canister
Leaking EVAP hose or tube
Wiring issues in EVAP circuit
Cracked or damaged fuel tank

Diagnosis Steps

1Connect an OBD-II scanner and read all stored trouble codes and freeze frame data
2Inspect and tighten the gas cap; replace if damaged or worn
3Perform a smoke test on the EVAP system to locate leaks
4Inspect all EVAP hoses and connections for cracks or disconnections
5Test the purge valve and vent valve with a multimeter and vacuum pump

Estimated Repair Cost

$50 — $600

Cost varies by vehicle, location, and repair shop. Includes parts and labor.

Commonly Affected Vehicles

Toyota CamryHonda CivicHyundai SonataSubaru Outback

Related Codes

P0441 P0440 P0455

More Evaporative Codes

P0440Evaporative Emission Control System Malfunction

Moderate

P0441Evaporative Emission Control System Incorrect Purge Flow

Moderate

P0442Evaporative Emission Control System Leak Detected (Small Leak)

Low

P0443Evaporative Emission Control System Purge Control Valve Circuit

Moderate

P0444Evaporative Emission Control System Purge Control Valve Circuit Open

Moderate

P0445Evaporative Emission Control System Purge Control Valve Circuit Shorted

Moderate

Frequently Asked Questions

Yes, a loose, damaged, or missing gas cap is one of the most common causes of EVAP system codes. Always try tightening the gas cap first and driving for a few days to see if the code clears.