EVAP Purge Control Valve Circuit High
The P0459 code indicates that the Powertrain Control Module (PCM) has detected a high voltage condition in the purge control valve circuit. This valve is part of the evaporative emission (EVAP) system, which prevents fuel vapors from escaping into the atmosphere. The purge valve opens to allow stored vapors to be drawn into the engine for combustion. A high voltage signal suggests a short to power, a faulty valve, or a wiring issue.
01. Most Common Causes
- Faulty purge control valve
- Short to power in the purge valve circuit
- Damaged wiring or connector
- Corroded terminals
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light on
- Possible rough idle or hesitation
- Fuel odor
- Failed emissions test
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the purge valve wiring and connector for damage or corrosion.
Step 3: Test the purge valve resistance with a multimeter (typically 20-30 ohms).
Step 4: Check for voltage at the valve connector with key on; should be battery voltage on one pin.
Step 5: If voltage is present on both pins or no ground signal, repair short or replace valve.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but it may cause rough idle and increased emissions. It's best to repair soon to avoid failing an emissions test.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, depending on the cause. A purge valve replacement is often around $100.