Faulty EVAP purge control valve/solenoid (35% likelihood): An internally failed purge solenoid can present high resistance or an open circuit, causing the PCM to see higher-than-expected voltage on the control circuit. Open circuit or broken wire in purge valve harness (30% likelihood): A broken, disconnected, or damaged wire in the purge valve circuit creates an open that reads as high voltage to the PCM. Corroded or disconnected connector (20% likelihood): Corrosion or a disconnected plug at the purge solenoid prevents proper grounding, resulting in a high-voltage reading at the PCM. Short to battery voltage in the signal wire (10% likelihood): The purge valve control wire may be shorted to a power source, causing constantly high voltage regardless of PCM commands. PCM/ECM malfunction (5% likelihood): In rare cases, the PCM's internal driver for the purge valve may malfunction, incorrectly reporting a high circuit condition.

How much does it cost to fix P0459?

DIY repair typically costs $20–$80 for parts. Professional repair runs $150–$400 including parts and labor.

P0459

Powertrain

Low

Evaporative Emission System Purge Control Valve Circuit High

Get Your FREE AI Diagnostic Report

Enter your vehicle for a personalized diagnosis for code P0459

The P0459 code means the PCM has detected higher-than-expected voltage in the EVAP purge control valve circuit. This is the companion code to P0458 (low circuit). The purge valve controls the flow of fuel vapors from the charcoal canister into the engine's intake manifold. A high circuit reading typically indicates an open circuit, a disconnected connector, or a failed solenoid rather than a vapor leak problem.

As with most EVAP electrical codes, you probably won't notice significant drivability issues. The Check Engine light will be on, and there could be a faint fuel smell in some cases, but the engine should run normally. Your car will fail an emissions test with this code present.

Diagnosis starts with a visual inspection of the purge valve connector — make sure it's fully seated and free of corrosion. Next, check the wiring for breaks, fraying, or damage. If the wiring and connector look good, the purge solenoid itself is likely the culprit. Most purge valves are inexpensive parts ($20–$60) and are mounted in accessible locations near the intake manifold, making this a straightforward replacement for most DIYers.

Severity

Low — MonitorThis Month

Symptoms

•Check Engine light is on
•Slight fuel odor from the engine area
•Minor reduction in fuel economy
•Occasional rough idle at startup

Likely Causes

Faulty EVAP purge control valve/solenoid35%

An internally failed purge solenoid can present high resistance or an open circuit, causing the PCM to see higher-than-expected voltage on the control circuit.

Open circuit or broken wire in purge valve harness30%

A broken, disconnected, or damaged wire in the purge valve circuit creates an open that reads as high voltage to the PCM.

Corroded or disconnected connector20%

Corrosion or a disconnected plug at the purge solenoid prevents proper grounding, resulting in a high-voltage reading at the PCM.

Short to battery voltage in the signal wire10%

The purge valve control wire may be shorted to a power source, causing constantly high voltage regardless of PCM commands.

PCM/ECM malfunction5%

In rare cases, the PCM's internal driver for the purge valve may malfunction, incorrectly reporting a high circuit condition.