Number 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
Can you drive with P0448?
Severity: Plan the repair. Yes — this is an emissions-system fault. The car will generally drive normally, but it will fail an emissions inspection with the light on.
If you ignore it: Fuel economy and emissions creep up, and some faults in this family (rich/lean running) stress the catalyst over time.
This is the #81 most common code in our top-150 library, in the evap — fuel vapor system family (Powertrain system). Severity is Number Nest's editorial triage — if the light is flashing or the car feels unsafe, stop driving it whatever any page says.
What P0448 means
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.
Systems involved: EVAP vent valve, vent valve wiring, charcoal canister, engine control module (ECM/PCM).
Causes, ranked by likelihood
| # | Cause | Likelihood |
|---|---|---|
| 1 | Vent valve or vent path blocked by dust, dirt or water (Nissan reading) | most likely |
| 2 | Vent valve coil shorted (below 1 Ω) | possible |
| 3 | Control wire shorted to positive | possible |
| 4 | Module driver damaged | less common |
Check them in order — the list is ranked so the likely, cheaper causes come before the expensive part.
Symptoms you may notice
- Check engine light on
- Refuelling problems if the vent is blocked
- EVAP leak test does not run
Misdiagnosis traps
- Replacing the part named by the code title without testing. The code reports a failed self-test; the cause list above is ranked so the likely, cheap causes are checked before the expensive part is condemned.
- Clearing the code and declaring victory when the light stays off for a day — the monitor that sets this code runs only under specific driving conditions.
(General diagnostic guidance for this code family — no code-specific trap is published for this code.)
How a good shop confirms it
- Confirm the code and record any companion codes — companions narrow the system fast.
- Inspect the affected components and their wiring/connectors for damage, corrosion and looseness.
- Test the top-ranked cause with live data or a multimeter before replacing anything.
(Standard diagnostic path for this family, labeled as general guidance.)
Repair options & costs
| Repair | Shop total (parts + labor) | DIY (parts only) | Difficulty |
|---|---|---|---|
| EVAP purge valve / solenoid | $68 – $198 | $30 – $110 (parts only) | 1/5 |
| EVAP leak diagnosis (smoke test) + gas cap | $73 – $248 | $10 – $60 (parts only) | 1/5 |
National ranges from Number Nest's cost model (midsize car, independent shop, US-average labor). Published cross-check — EVAP purge valve / solenoid: CarMD 2026 national average $172.
OBDex repair data for this code rates the job difficulty medium with a typical labor time in the 0.5–3 hour range and DIY possible: see the guide above.
Price this repair in your state
Estimated total: — (midsize car, independent shop)
Frequently asked questions
How much does it cost to fix P0448?
The fix most associated with this code — evap purge valve / solenoid — runs $68 – $198 at an independent shop for a midsize car in our cost model (parts + labor, US average). The code names a system, not a part, so confirm the cause before spending: the ranked causes above are ordered by likelihood.
Can I drive with P0448?
See the can-you-drive verdict above — it is based on the system involved and the cascading-damage risk, and it is our editorial triage, not a manufacturer instruction. If the light is flashing or the car feels unsafe, stop driving it regardless of any code.
Will P0448 clear itself?
If the fault was a one-off (a loose cap, a cold-start glitch), the light can go out after several clean trips and the code ages into history. A fault that is still present re-sets the code as soon as the car runs that self-test again — monitors run under specific conditions, which is why "it hasn't come back in two days" is not proof of a fix.
Will my car fail inspection with P0448?
In states with OBD-based emissions inspection, yes — an illuminated check-engine light or an incomplete readiness monitor fails the test regardless of what the tailpipe would show. C-codes (ABS) fall under safety inspection instead in states that have one.
What should I check first for P0448?
The first item on the ranked-causes list above — it is ranked likelihood-first for exactly this reason — plus the free checks: recent work in the area (connectors left loose are a classic), fluid levels, and the battery and grounds on electrical codes.
Where this data comes from
Code facts, causes and symptoms come from OBDex — an open dataset of independently authored descriptions of the standardized generic OBD-II codes (CC0 1.0, public domain; github.com/foerbsnavi/OBDex). The SAE J2012 document itself is copyrighted and is not reproduced here. Cost ranges are Number Nest's own US planning model: national parts and labor ranges cross-checked against the CarMD Vehicle Health Index 2026 published averages, with labor adjustable by the BLS OEWS May 2025 state wage index for auto technicians (occupation 49-3023) — a wage index, not a surveyed shop rate. Severity and can-you-drive notes are our editorial triage, not a manufacturer instruction.