P0459 EVAP Emission System Purge Control Valve Circuit High
OBD-II Trouble Code Technical Description
Evaporative Emission System Purge Control Valve Circuit High
This diagnostic trouble code (DTC) is a generic powertrain OBD-II code. It is considered generic because it applies to OBD-II equipped vehicles, including but not limited to Hyundai, VW, Chevrolet, Audi, Kia, Volvo, BMW, etc. Anecdotally it seems more common on Subaru & Ford models. Specific repair steps may vary depending on the year, make, and model of vehicle.
What does that mean?
On vehicles equipped with evaporative emission control systems (EVAP), the engine draws in excessive fuel vapors from the gas tank that would otherwise be vented into the atmosphere. The purpose of the system is to reduce vehicle emissions.
The evaporative emission system consists of the fuel tank, a vacuum hose to the charcoal canister for containing the fuel vapors, pressure sensor on the fuel tank, purge valve on the charcoal canister, vacuum hose to the filler neck shut off valve and vacuum hose from the charcoal canister purge valve to the intake manifold. When the engine is off, the vent shutoff valve and canister purge valve are closed.
The fuel can't escape into the atmosphere. When the engine starts, the purge valve on the canister opens to allow the trapped fuel vapor to be drawn by engine vacuum into the intake manifold. At the same time the vent shutoff valve also opens to allow a small amount of air to enter the canister and mix with the fuel vapor for a better mixture. Once vented and the pressure sensor in the tank shows a significant drop, both valves close sealing the system once again.
The fuel vapor is routed through a vacuum line to the engine's intake and the purge valve/solenoid meters the desired amount of fuel vapors, controlled by the vehicles powertrain control module (PCM) or engine control module (ECM). The PCM/ECM monitors the voltage to the purge control valve and has detected a higher voltage than expected.
Related purge control valve circuit codes include:
P0443 Evaporative Emission Control System Purge Control Valve Circuit P0444 Evaporative Emission Control System Purge Control Valve Circuit Open P0445 Evaporative Emission Control System Purge Control Valve Circuit Shorted P0458 Evaporative Emission System Purge Control Valve Circuit LowSymptoms
Noticeable symptoms of a P0459 EVAP trouble code normally only include illumination of the malfunction indicator lamp (MIL), or "Check Engine Light / Service Engine Soon" light. Other trouble codes may accompany this code. In some cases there may be a smell of gas and/or a slightly decline in fuel efficiency.
Potential Causes
Causes of this DTC may include:
Faulty fuse or relay Faulty purge control valve Faulty EVAP purge solenoid control Engine wiring harness or connector electrical circuit problem Purge control solenoid electrical circuit problem PCM/ECM malfunctionDiagnosis & Repair
A good first step if you receive a P0459 is to check for Technical Service Bulletins (TSBs) that apply to your year/make/model. If this is a known issue, a TSB can help save you time and money during diagnosis & repair.
Visually inspect the engine wiring harness connectors for damage, look for pinched wires, loose or bent pins or bare wiring with no insulation. Typically the purge control valve is energized by the the battery and triggered on and off with a duty cycle through the PCM/ECM. Using the manufacturers wiring diagrams, identify which type of circuit being used and check for battery voltage presence with the key on/engine off at the power side of the control solenoid connector using a digital volt ohm meter (DVOM) set to the volts scale. If no battery voltage is present, trace the wiring back to determine the cause.
Check for a short to ground by di
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