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.
What causes the P0448 code?
Some of the most common reasons that a P0448 code may be stored include:
- A damaged or defective vent valve
- An imprperly installed or defective fuel cap
- A clogged or faulty charcoal canister
- A damaged purge control solenoid
- Cracks in the fuel vapor or vacuum hoses
- A problem with the wiring or circuit for the vent valve
- A problem with the PCM (rare)
Often, the problem can be traced to a leak in a vacuum hose or a problem with the fuel cap.