P0448Generic code

P0448 Code: Evaporative Emission Control System Vent Control Circuit Shorted

The P0448 code indicates a short in the EVAP vent valve circuit: the current is higher than normal or the circuit is grounded. Check the fuse, relay, connector and wiring before replacing the valve, because they are the most common cause. The code usually does not affect driving.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$30 to $250
Difficulty
Medium
System
Emissions Control
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0448 code means

The vent valve lets clean air into the canister and closes during the leak test. It is open at rest, and the computer closes it when it needs to seal the system.

The computer monitors the control circuit from its own driver transistor. The P0448 code indicates a short: the current is higher than normal or the circuit is shorted to ground. Before replacing the component, check the fuse, relay, connector and wiring, since they are the most common cause.

The valve usually sits next to the canister under the vehicle, exposed to dust and water. A valve that will not open makes the pump nozzle shut off while you fuel up, and one that will not close makes the leak test impossible.

Measure the resistance of the component. A reading well below specification points to shorted windings. Also check the insulation of each wire to ground with the connector unplugged. It should read infinite.

P0448 code symptoms

  • Check engine light on.
  • The pump nozzle shuts off while fueling.
  • EVAP monitor incomplete.

Likely causes of the P0448 code

  1. Shorted coil with very low resistance.
  2. Wire shorted to ground from the insulation rubbing against the chassis.
  3. Water in the connector. Very common on components mounted under the vehicle.

How to diagnose the P0448 code step by step

  1. Command the component with the scan tool and check whether it responds.
  2. Check the fuse and relay.
  3. Measure the supply at the connector: battery voltage with the key on or when it is commanded.
  4. Measure the component resistance and compare it with the manual. Also check the insulation to ground.
  5. Check the control wire for continuity and for shorts.
  6. Inspect the vent filter and clean off any dirt.
  7. Power it with 12 V. It should close with a click.

How to fix the P0448 code

  • Repair the connector, the wiring or the power supply.
  • Replace the EVAP vent valve if it does not respond with correct power and control.
  • Clear the codes and verify that the monitor completes.

Technical reference data

  • 12 V solenoid; approximate resistance 20 to 30 ohms.
  • Approximate values only: check the manufacturer data for your engine.

Brand-specific notes

The vent valve normally sits next to the canister under the vehicle, so start with the connector and the wiring before you buy the part.

P0448 on GM

On GM vehicles the vent valve often gets clogged on vehicles that are driven on dirt roads.

P0448 on Toyota

On Toyota vehicles the vent valve often gets clogged on vehicles that are driven on dirt roads.

Frequently asked questions about P0448

Can I drive with a P0448 code?
Yes. A P0448 code normally does not affect driving. Repair it before your emissions inspection.
What does the EVAP vent valve do?
The vent valve lets clean air into the canister and closes during the leak test. It is open at rest, and the computer closes it when it needs to seal the system.
Do I always have to replace the part?
No. Check the fuses, relays, connectors and wiring first.
How much does it cost to fix P0448?
Roughly $30 to $250, depending on whether it is wiring or the valve itself.
What does the P0448 code mean?
It is a generic OBD2 code that means the EVAP vent valve circuit is shorted: the current is higher than normal or the circuit is grounded.
What is the most common cause of P0448?
Wiring and connector problems, such as a wire rubbed against the chassis or water in the connector, are more common than a bad valve. Check those first.

Related codes

Questions about the P0448 code

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