EVAP Purge Control Valve Circuit High
The P0459 code indicates a high voltage condition in the purge control valve circuit of the evaporative emission (EVAP) system. The powertrain control module (PCM) monitors the voltage across the purge valve solenoid. When the voltage is higher than expected (e.g., above 4.5V), it sets this code. This typically points to a short to power, a faulty purge valve solenoid, or an issue with the wiring/connector.
1. Most Common Causes
- Short to power in purge valve circuit
- Faulty purge valve solenoid
- Damaged wiring or connector
- Corroded terminals
- Faulty PCM (rare)
2. Symptoms You Will Notice
- Check Engine Light on
- Possible rough idle
- Possible fuel smell
- Possible failed emissions test
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect purge valve connector and wiring for damage or corrosion.
Step 3: Disconnect purge valve connector; measure voltage at harness side with key on. Should be 0V. If battery voltage, repair short to power.
Step 4: Test purge valve solenoid resistance (typically 10-30 ohms). Replace if out of spec.
Step 5: Clear code and test drive; if returns, check PCM for faults.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but it may cause rough idle, increased emissions, and potential fuel vapor leaks. It's best to repair promptly.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, depending on the cause. A purge valve replacement costs around $30-$80, plus diagnostic time.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.