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.
How the engine computer detects it
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.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on
- Refuelling problems if the vent is blocked
- EVAP leak test does not run
Common causes
- Vent valve or vent path blocked by dust, dirt or water (Nissan reading) Most likely
- Vent valve coil shorted (below 1 Ω) Possible
- Control wire shorted to positive Possible
- Module driver damaged Less likely
How to diagnose P0448
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: evap vent valve, vent valve wiring, charcoal canister, engine control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P0448 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Nissan Frontier | 2007–2018 | 4 | 51k |
Counts of owner complaints to the NHTSA that mention P0448 (7 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 4
- Auxiliary emission controls
- 48
- Specific fault
Questions drivers ask
Can I drive with code P0448?
Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.
Will my car pass an emissions inspection with P0448?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0448 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.