P0459 – EVAP Purge Solenoid Circuit High

Urgency and Driving Considerations

When the P0459 code is triggered, it indicates an issue with the evaporative emission (EVAP) system purge control valve circuit. In most cases, you can continue driving the vehicle as this is not an immediately critical issue. However, it's best to diagnose and repair the problem promptly to ensure proper functioning of the EVAP system and to prevent potential damage to other components. If you notice any strong fuel odors or significant decrease in fuel efficiency along with the check engine light, it's advisable to have the vehicle inspected by a mechanic as soon as possible.

Code Details

The P0459 is a generic OBD-II code that applies to vehicles equipped with OBD-II, including various makes such as Hyundai, VW, Chevrolet, Audi, Kia, Volvo, BMW, etc. It seems to be more commonly observed in Subaru and Ford models. The specific repair steps may vary slightly depending on the vehicle's year, make, and model.

System and Components Involved

The evaporative emission system is designed to capture and prevent fuel vapors from escaping into the atmosphere. Key components include:

• Fuel tank
• Charcoal canister to contain fuel vapors
• Pressure sensor on the fuel tank
• Purge valve/solenoid on the charcoal canister
• Vent shut off valve
• Vacuum hoses connecting components
• Powertrain control module (PCM) or engine control module (ECM)

The purge valve/solenoid controls the amount of fuel vapors routed to the engine's intake. The PCM/ECM monitors the voltage to this valve.

Common Causes

Potential causes of a P0459 code include:

• Damaged or loose gas cap
• Faulty purge control valve/solenoid
• Short or open in the purge valve circuit wiring
• Damaged or disconnected vacuum hoses
• Malfunctioning charcoal canister
• Issues with the PCM/ECM

Diagnosis Steps

1. Check for any applicable Technical Service Bulletins (TSBs) for your vehicle.
2. Visually inspect wiring harness connectors for damage, loose/bent pins, or exposed wiring.
3. Using a digital volt ohm meter (DVOM), check for battery voltage at the power side of the purge valve connector with the key on, engine off.
4. Test for shorts to ground in the power and control side wiring using the DVOM set to ohms.
5. Check the purge valve itself for proper resistance and shorts.
6. Using an advanced scan tool, monitor the EVAP system operation during a road test and verify PCM/ECM commands.

Repair Solutions

Common repairs for a P0459 code include:

• Inspecting and properly reinstalling the gas cap
• Replacing the gas cap if damaged
• Replacing the purge control valve/solenoid
• Repairing damaged wiring or loose connections
• Replacing faulty vacuum hoses
• Addressing any issues with the charcoal canister
• Reprogramming or replacing the PCM/ECM in rare cases

Prevention and Costs

To help prevent P0459 issues:

• Always ensure the gas cap is tight after refueling
• Address any damage to the EVAP system promptly
• Maintain the fuel system components properly

Repair costs can vary widely depending on the root cause, ranging from under $20 for a gas cap to over $500 for a PCM/ECM, with most repairs falling in the $100-300 range. Typical part costs are:

• Gas cap: $15-30 USD / €13-26 EUR
• Purge valve: $90-200 USD / €77-172 EUR
• Charcoal canister: $180-650 USD / €155-560 EUR
• PCM/ECM: $500-1400 USD / €430-1200 EUR

Related Issues

Other EVAP system related codes that may appear along with P0459 include P0440, P0441, P0442, P0443, P0446, P0447, P0448, P0455, P0456, and P1450. It's not uncommon for multiple EVAP codes to be triggered simultaneously if there is a significant leak or electrical issue.

Frequently Asked Questions About P0459 Trouble Code

What does the P0459 trouble code mean?

The P0459 trouble code indicates that the powertrain control module (PCM) has detected a high voltage condition in the evaporative emission (EVAP) system's purge control valve circuit. This means there is an electrical issue causing excessive voltage to the purge valve.

What are the common symptoms of a P0459 code?

Common symptoms include:

• Check engine light is on
• Fuel smell from the vehicle
• Slightly decreased fuel efficiency

In most cases, there are no noticeable driveability issues. The check engine light is often the only symptom.

What are the potential causes of a P0459 code?

Potential causes of a P0459 code include:

• Damaged or loose gas cap
• Faulty purge control valve/solenoid
• Short or open circuit in the purge valve wiring
• Damaged or disconnected vacuum hoses
• Malfunctioning charcoal canister
• Issues with the PCM

Is it safe to drive with a P0459 code?

In most cases, you can continue driving the vehicle as this is not an immediately critical issue. However, it's best to diagnose and repair the problem promptly to ensure proper EVAP system function and prevent potential damage to other components.

Can a loose or faulty gas cap cause a P0459 code?

Yes, a damaged, loose, or missing gas cap can cause a P0459 code. The gas cap seals the EVAP system, so if it's not sealing properly, it can trigger EVAP system related codes like P0459. Always check the gas cap first when diagnosing P0459.

What is the EVAP system purge control valve and what does it do?

The EVAP purge control valve, also known as a purge solenoid, controls the flow of fuel vapors from the charcoal canister to the engine's intake manifold. It is controlled by the PCM and allows the engine to "purge" the vapors from the EVAP system when conditions are correct.

How do you diagnose a P0459 code?

To properly diagnose a P0459 code:

1. Check for applicable technical service bulletins (TSBs).
2. Visually inspect wiring and connectors for damage.
3. Test purge valve circuit voltage and resistance with a multimeter.
4. Check purge valve for proper operation.
5. Inspect vacuum hoses for leaks or damage.
6. Verify proper EVAP system operation with a scan tool.

Can a malfunctioning charcoal canister cause a P0459 code?

Yes, a faulty charcoal canister can cause a P0459 code. The charcoal canister is a key component of the EVAP system that stores fuel vapors. If it has an issue like a leak or clog, it can trigger EVAP system codes like P0459.

What repairs are commonly needed to fix a P0459 code?

Common repairs for a P0459 code include:

• Replacing a faulty gas cap
• Replacing the purge control valve
• Repairing damaged wiring or connectors
• Replacing damaged vacuum hoses
• Replacing a malfunctioning charcoal canister
• Reprogramming or replacing the PCM (rare)

How much does it typically cost to repair a P0459 code?

The cost to repair a P0459 code varies widely depending on the root cause. It can range from under $20 for a new gas cap to over $500 to replace a PCM. Most common repairs like replacing a purge valve or wiring harness fall in the $100-300 range.

Can a P0459 code cause a vehicle to fail an emissions test?

Yes, a P0459 code can cause a vehicle to fail an emissions test. The EVAP system is a critical emissions control system, so any issues with it like a P0459 code will likely result in a failed emissions test. The code must be repaired and the system must be functioning properly to pass.

Is a P0459 code the same on all vehicle makes and models?

The P0459 is a generic code, which means it has the same basic meaning for all vehicles equipped with OBD-II. However, the specific repair procedures, component locations, and technical service bulletins can vary between different vehicle makes and models. Always consult vehicle-specific repair information when diagnosing and repairing a P0459 code.

Can a weak battery or charging system cause a P0459 code?

Potentially, yes. While it's not the most common cause, a weak battery or malfunctioning charging system can cause a P0459 code in some cases. Low system voltage can cause erratic purge valve operation which may trigger the code.

What is the difference between a P0459 and a P0455 code?

While both P0459 and P0455 are EVAP system related codes, they indicate different issues:

• P0459 indicates a high voltage condition specifically in the purge valve circuit.
• P0455 indicates a large leak detected somewhere in the EVAP system.

The diagnosis and repair steps are different for each code, although there can be some overlap in potential causes like a faulty gas cap.

Can a P0459 code be caused by a recent repair or service?

Yes, a P0459 code can be triggered by a recent repair if the EVAP system components were disturbed or reinstalled incorrectly. Common examples include failing to properly reconnect the purge valve after an intake manifold service, or not fully tightening the gas cap after refueling. If you have a P0459 code shortly after a repair, double check the work in that area.

How do you test an EVAP purge control valve?

To test an EVAP purge control valve:

1. Locate the valve, typically on the charcoal canister or near the intake.
2. Disconnect the electrical connector and test the valve's resistance with a multimeter. Compare to specifications.
3. Apply battery voltage to the valve terminals and listen for a clicking sound indicating the valve is opening and closing.
4. If resistance is out of spec or the valve doesn't click, it needs to be replaced.

What causes an open circuit in the purge valve wiring?

Common causes of an open circuit in the purge valve wiring include:

• Rubbed through or chaffed wiring insulation
• Broken wires due to fatigue
• Poor connection at the purge valve connector or PCM
• Corrosion in the wiring connectors
• Damage from rodents chewing on wiring
• Previous damage during a repair

Open circuits can be located by visually inspecting the wiring and testing continuity with a multimeter.

What causes a short circuit in the purge valve wiring?

Common causes of a short circuit in the purge valve wiring include:

• Wiring insulation damaged and allowing contact with metal
• Pins in the purge valve or PCM connector bent and touching
• Metallic debris shorting the terminals in the connector
• Aftermarket accessories improperly spliced into the wiring
• Water intrusion into the connectors

Short circuits can be located by visually inspecting the wiring and connectors and testing resistance to ground with a multimeter.

Can a P0459 code keep coming back after repairs?

Yes, it's possible for a P0459 code to keep returning after repairs for a few reasons:

• The original diagnosis was incorrect and the root cause was not repaired.
• There are multiple issues present, such as a wiring problem and a faulty purge valve.
• The replacement parts used were defective or of poor quality.
• There was an error made during the repair, like damaging the new part.
• The code was not properly cleared from the PCM after the repair.

If a P0459 code persists after repairs, it's best to recheck the original diagnosis and repair quality. If the problem continues, more advanced diagnosis with a scan tool and oscilloscope may be needed.

What should you do if you keep getting a P0459 code?

If you keep getting a P0459 code, even after attempted repairs, you should:

1. Double check the repairs to ensure the problem was properly diagnosed and parts were installed correctly.
2. Visually reinspect the wiring harness and connectors for any damage.
3. Test the purge valve circuit again with a multimeter for proper voltage and resistance.
4. Verify the new purge valve is working correctly.
5. Check for any new technical service bulletins that may apply.
6. Perform a smoke test of the EVAP system to check for any leaks.
7. Consider taking your vehicle to a professional technician or dealership for more advanced diagnosis with a scan tool and oscilloscope.

Persistent P0459 codes can be frustrating, but careful diagnosis and quality repairs can resolve the issue. If you're unsure about your diagnosis or repair skills, it's best to seek out a professional opinion.