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P0448 is a diagnostic trouble code (DTC) for "Evaporative Emission Control System Vent Control Circuit Shorted". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
P0448 OBD-II Trouble Code: Evaporative Emission Control System Vent Control Circuit Shorted
The P0448 code is stored when the powertrain control module (PCM) detects that the circuit for the evaporative emission control system’s vent has shorted, or that the valve for this system is stuck in the closed position.
When gas sits in the gas tank, it emits vapor. As you drive your vehicle, the evaporative emission control system’s vent opens up to allow those vapors to circulate through to the charcoal canister, the outside of the vehicle, or the engine’s intake manifold (depending on what kind of vehicle you have). If this vent valve is stuck closed or there is a short in its circuit preventing it from opening, the PCM will store a P0448 code, and the Check Engine Light will come on.
Some of the most common reasons that a P0448 code may be stored include:
In most cases, the only noticeable symptom will be the illuminated Check Engine Light. However, even though other symptoms may not be in evidence, there will likely be other related codes stored by the PCM, as well.
The first step in diagnosing a P0448 code is to use an OBD-II scanner to read any and all codes stored by the PCM. If other related codes are stored, they should be dealt with first. Then, the mechanic will move on to diagnose the issues causing the P0448 code to be stored.
They may start by checking the fuses, as a blown fuse could be preventing the vent solenoid from operating. After checking the fuses, they’ll check the circuit for any chafed, corroded, or otherwise damaged wires in the wiring harness, and they’ll check the connectors to ensure they’re not corroded and that all connections are solid.
Using an ohmmeter, they may check that the voltage is consistent throughout the circuit. Upon resolving any issues with the vent valve and/or its circuit, they’ll clear all codes and then retest the system to ensure that the code isn’t saved again.
Often, the problem can be traced to a leak in a vacuum hose or a problem with the fuel cap. In many cases, though, inexperienced mechanics and vehicle owners will miss these potentially simple fixes and spend a lot of time and money trying to make repairs that won’t actually fix the problem.
As we mentioned, some of the most common causes for a P0448 code to be stored involve a faulty gas cap and/or a leak in one of the hoses. Replacing these components may solve the problem without any further work. Other common solutions include:
If you have a Chrysler, Jeep, or Dodge vehicle that has set a P0448, there’s a good chance that you have a bad vent. GM has released an improved valve assembly to handle this problem, as well. Whatever type of vehicle you have, if you want to ensure that your vehicle passes an OBD-II emissions test, you’ll have to get this issue taken care of and clear all codes from your PCM.
YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.