P0448: EVAP System Vent Control Circuit Shorted

The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. P0448 is the short-circuit code of the older scheme for the vent valve. Subaru (also in the Saab 9-2X) expects supply voltage above 10 V at the module output with the valve off; a short to positive or a coil below 1 Ω sets the code after two drives, and Subaru then also replaces the module, as its driver may be damaged. Nissan and Infiniti use P0448 differently, for a vent valve or vent path stuck closed by dust or water, with replacement of canister, valve and filler tube. GM and Ford do not use the code.

Low severity. Can I keep driving?Yes, you can normally keep driving. If there is a strong smell of gasoline, find the leak before continuing and do not smoke nearby.

Symptoms

Check engine light on
Refuelling problems if the vent is blocked
EVAP leak test does not run

Most likely causes

Vent valve or vent path blocked by dust, dirt or water (Nissan reading)
Vent valve coil shorted (below 1 Ω)
Control wire shorted to positive
Module driver damaged

What to check, in order

Start with the simplest. You can tick off each step.

Start with the fuel cap: tighten it fully and check its seal
Inspect the hoses and connections around the tank and the charcoal canister
Use the scanner to test the purge and vent solenoid valves
Run a smoke test to find small leaks

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P0448 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
4: Emissions
48: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0448?

Yes, you can normally keep driving. If there is a strong smell of gasoline, find the leak before continuing and do not smoke nearby.

What causes code P0448?

The most common causes are: vent valve or vent path blocked by dust, dirt or water (Nissan reading); vent valve coil shorted (below 1 Ω); control wire shorted to positive.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.