What does it mean?
On vehicles equipped with Evaporative Emission Control (EVAP) systems, the engine draws excess fuel vapors from the gas tank that would otherwise be released into the atmosphere. The purpose of the system is to reduce vehicle emissions.
The evaporative emission system consists of the fuel tank, a vent line to the charcoal canister to contain fuel vapors, a pressure sensor on the fuel tank, a purge valve on the charcoal canister, a vent line to the fill neck shut-off valve, and a vent line from the charcoal canister purge valve to the intake manifold. When the engine is off, the vent shut-off valve and the tank purge valve are closed.
Fuel cannot escape into the atmosphere. When the engine starts, the purge valve on the tank opens to allow trapped fuel vapor to be drawn by engine vacuum into the intake manifold. At the same time, the vent shut-off valve also opens to allow a small amount of air to enter the tank and mix with the fuel vapor for better combustion. Once purged and the pressure sensor in the tank shows a significant drop, both valves close again, sealing the system.
The fuel vapor is routed via a vacuum line to the engine intake, and the purge valve/solenoid measures the desired amount of fuel vapors, controlled by the Powertrain Control Module (PCM) or Engine Control Module (ECM). The PCM/ECM monitors the voltage to the purge control valve and detected a voltage lower 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
P0459 Evaporative Emission System Purge Control Valve Circuit High
Symptoms
Visible symptoms of a P0458 EVAP trouble code typically include only the illumination of the Malfunction Indicator Lamp (MIL) or the “Check Engine/Service Engine Soon” light. Other trouble codes may accompany this code. In some cases, there may be a gas smell and/or a slight decrease in fuel efficiency.
Potential causes
Causes
of this DTC may include:
Faulty fuse or relay
Defective purge control valve
Faulty EVAP purge solenoid control
Open or shorted engine wiring harness or connector
Open or shorted purge control solenoid
PCM/ECM malfunction
Diagnosis and Repair
A good first step if you receive a P0458 is to check for Technical Service Bulletins (TSBs) that apply to your vehicle’s year/make/model. If it is a known issue, a TSB can save time and money during diagnosis and repair.
Visually inspect the engine wiring harness connectors for any damage, look for pinched wires, loose or bent pins, or bare wiring without insulation. Typically, the purge control valve is powered by the battery and triggered on and off with a duty cycle via the PCM/ECM. Using the manufacturer’s wiring diagrams, identify the type of circuit used and check for battery voltage with the key on/engine off on 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 to determine the cause.
Check for a short to ground by disconnecting the harness from the control valve solenoid and the voltage source. Using the DVOM set to the ohms scale, with the negative lead connected to a known good ground and the positive lead to each end that powers the control valve solenoid. If resistance is very low, suspect a short to ground and repair the wiring harness. Check for a short to ground on the control side of the harness by disconnecting the harness from the control valve solenoid and the PCM/ECM harness. Identify the correct wire and using the DVOM set to an ohms scale, check resistance with the negative lead connected to a known good ground and the positive lead on one of the control circuit wire bundles. If resistance is very low, suspect a short to ground and repair the wiring harness.
Purge Control Solenoid – Check continuity at the purge control solenoid connector pins after removing the plug from the harness using the DVOM set to the ohms scale. Verify that resistance meets manufacturer specifications. Check for a short to ground using the DVOM with the negative lead attached to a known good ground and the positive lead on each of the control valve solenoid terminal pins. Resistance should be very high or above the limit (OL). If very low resistance is detected, suspect the control valve solenoid is shorted to ground and replace it with a known good unit.
Since the EVAP system only activates under certain driving conditions, it will be necessary to monitor EVAP control operation using a capable advanced scan tool and perform a road test under the required driving conditions to activate the EVAP system. Some