P0448: EVAP Vent Control Circuit Shorted
P0448 means the car's computer found a problem with the vent valve of the evaporative emission (EVAP) system, either an electrical short in its circuit or a vent that is stuck closed. It turns on the check engine light and usually does not affect how the car drives, but it needs repair to keep the EVAP system working and to pass an emissions test.
You can drive, but get it checked soon
The data lists no limp mode for this code, so the car should keep running normally. If the vent is blocked, you may have trouble refueling, and the EVAP system will not be tested or working properly until it is fixed, so have it checked soon.
What it means
The EVAP system catches fuel vapor from the tank in a charcoal canister, and the engine later draws that vapor off through a purge valve. A vent valve opens the canister to fresh air. P0448 is tied to that vent valve, and the meaning depends on the brand. On Subaru (and the Saab 9-2X), the computer expects more than 10 V at the module output with the valve off. A short to positive voltage, or a valve coil reading below 1 Ω (ohm, a unit of electrical resistance), sets the code after two drives. On Nissan and Infiniti, the code is used when the vent valve or vent path is stuck closed by dust or water. GM and Ford do not use this code.
Likely causes
- Vent valve or vent path blocked by dust, dirt or water (Nissan reading)Very likely
On Nissan and Infiniti this code is set when the vent valve or vent path is stuck closed by dust or water.
- Vent valve coil shorted (below 1 Ω)Possible
A coil reading below 1 Ω is one of the conditions that sets the code on Subaru.
- Control wire shorted to positivePossible
A short to positive voltage on the valve's control wire pushes the voltage above the 10 V the computer expects with the valve off.
- Module driver damagedLess likely
A short can damage the driver inside the module, which is why Subaru also replaces the module in this case.
What you may notice
- Check engine light on
- Refueling problems if the vent is blocked
- EVAP leak test does not run
What to check, cheapest first
- 1Confirm the code with a scan tool and note whether it returns after clearing it and driving. The code needs two drives to set on Subaru. · you can do it
- 2Look at the vent valve wiring and connector for damage, rubbing, corrosion or water. · you can do it
- 3Check the vent valve and the vent path near the canister for dust, dirt or water blocking it. · mechanic
- 4Measure the vent valve coil resistance and compare it to the 1 Ω limit. · mechanic
- 5Check the control wire for a short to positive and the voltage at the module output with the valve off. · mechanic
- 6If the circuit is shorted, test the module driver and replace the module if it is damaged. On Nissan and Infiniti, the repair can include the canister, valve and filler tube. · mechanic
Related codes
Frequently asked questions
Can I drive with a P0448 code?+
Usually yes, since limp mode is not listed for this code. Get it checked soon, especially if refueling has become difficult.
Can a loose gas cap cause P0448?+
The data does not list the gas cap as a cause. This code points to the vent valve, its wiring or a blocked vent path.
Will P0448 pass an emissions test?+
Probably not. The code is emissions-relevant and turns on the check engine light, and the EVAP leak test may not run until it is repaired.
Can I fix it myself?+
The data rates DIY as not recommended. Repair is medium difficulty and estimated at 0.5 to 3 hours.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10