Diagnostic Trouble Code (DTC): P0458
P0458 code definition
The P0458 code means that a specific part of the EVAP system purge control valve circuit has caused a voltage reading that does not match the manufacturer’s specifications, and is therefore malfunctioning in some way.
What the P0458 code means
When this code is detected by the OBD-II scanner, it means that there is an issue with the EVAP emissions system. This system controls the rate of vapor from the canister with a system purge control valve. Part of the circuit system for this valve measures and reports voltage to the PCM. If this reading is lower than the manufacturer’s specifications, the PCM assumes that there is a fault in the circuit, and stores the P0458 code.
What causes the P0458 code?
In many cases, this code could be present due to an improperly installed fuel cap. However, there may be more complex issues behind this code, including:
- Faulty purge control solenoid
- Broken, clogged, or faulty charcoal canister
- Faulty vacuum hoses
- Faulty fuel vapor hoses
- Faulty pressure/flow sensor
- Open or shorted EVAP purge control solenoid harness
- Faulty, corroded, loose, open, or shorted electrical components in the EVAP emissions system purge control valve circuit, including wiring or connectors
What are the symptoms of the P0458 code?
Most of the time, there will be no other symptoms present when the P0458 code is present. The Check Engine Light may be lit, and there may be other codes stored in the PCM relating to the EVAP emissions control system.
How does a mechanic diagnose the P0458 code?
The first step to diagnosing the issue behind the P0458 code is to verify the code with an OBD-II scanner, and to check for other codes present. Similar or related codes may reveal a larger issue that should be addressed first.
After verifying, the next step is to perform a visual check of all the electrical wiring and components, to ensure that there is not a loose, shorted, or corroded wire that is causing the PCM to receive a faulty signal. Additionally, the mechanic may wish to check that the fuel cap is installed properly, because this is frequently a simple reason for the presents of the P0458 code.
Once these inspections have been performed, the code should be cleared and the system retested. If the code returns to the PCM, then the mechanic has diagnosed a larger issue with the EVAP emissions system purge control valve circuit, and should move on to further repairs.
Common mistakes when diagnosing the P0458 code
The most common mistake made when diagnosing the P0458 code is to replace system components without first inspecting the fuel cap or the vacuum hoses for improper installation or leaks. A thorough diagnostic procedure should be performed before system components are replaced.
How serious is the P0458 code?
The P0458 code does not represent a serious issue that will affect the operation of the vehicle; however, its presence may cause a vehicle to fail an emissions test. If the P0458 code is detected, it should be addressed at the next routine servicing if not before.
What repairs can fix the P0458 code?
After checking and repairing the electrical wiring, connectors, and other components, and ensuring that the fuel cap is properly installed and not damaged, the mechanic may perform other repairs that include:
- Replacing a faulty purge control solenoid.
- Repairing, cleaning, or replacing a broken, clogged, or faulty charcoal canister.
- Replacing faulty vacuum hoses.
- Replacing faulty fuel vapor hoses.
- Replacing a faulty pressure/flow sensor.
- Replacing or repairing an open or shorted EVAP purge control solenoid harness.
After each repair is made, the code should be cleared from the PCM and the system should be retested. This process allows the mechanic to eliminate potential causes until they discover exactly what was causing the code to be stored.
Need help with a P0458 code?
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