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DTC codes / Subaru codes / P1443

P1443 · SubaruEVAP Control System Vent Control Function Problem

P1443 on a Subaru indicates that the engine control module has detected a problem with the evaporative emission control system's vent control function, which typically involves the vent valve or its circuit. The computer monitors the vent valve's electrical circuit and its ability to seal or open the EVAP system during self-tests, and it sets this code when the expected response is not achieved.

SystemPowertrain
Code typeSubaru specific
SeverityLow
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms.
  • A slight fuel odor may be present around the rear of the vehicle if the vent valve is stuck open.
  • Difficulty refueling, such as the fuel nozzle clicking off repeatedly, if the vent system cannot relieve pressure.
  • A hissing or clicking sound from the rear of the vehicle when the vent valve is commanded to cycle.
  • In some cases, a rough idle or slight hesitation if the EVAP system leak affects engine vacuum.
  • No drivability issues in most cases, as the fault primarily affects emissions.

Common causes, most likely first

  1. Faulty EVAP vent valve (also called the vent solenoid) that is stuck open, stuck closed, or electrically failed.
  2. Damaged or corroded wiring or connector at the vent valve, often due to road debris or moisture.
  3. Failed EVAP pressure sensor or fuel tank pressure sensor sending incorrect signals to the ECM.
  4. Leaking or disconnected EVAP hose between the vent valve and the fuel tank.
  5. Clogged EVAP canister or vent filter restricting flow and causing the vent function to fail.
  6. ECM software issue or internal fault in the vent control driver circuit (rare).

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related EVAP codes to narrow down the circuit.
  2. Inspect the vent valve and its connector for physical damage, corrosion, or loose pins.
  3. Test the vent valve's electrical resistance and operation by applying 12 volts and listening for a click.
  4. Check the EVAP hoses and canister for cracks, clogs, or disconnections.
  5. Perform a smoke test on the EVAP system to check for leaks if the vent valve appears functional.
  6. If the valve fails electrical or functional tests, replace the vent valve and clear the code.
  7. After repairs, run the EVAP monitor to confirm the fix and ensure the code does not return.

Vent valve failures that fool technicians

  • A vent valve that clicks when bench-tested may still fail under operating conditions due to a weak spring or internal seal, so always test it on the vehicle with a scan tool command.
  • Corroded wiring at the vent valve connector is a common cause on older Subarus, especially in regions with road salt, and is often overlooked when replacing the valve.
  • A clogged EVAP canister can mimic a failed vent valve by preventing proper venting, so inspect the canister and filter before condemning the valve.
  • The ECM may set P1443 if the fuel tank pressure sensor is skewed, even when the vent valve is functioning correctly, so compare sensor readings with a known-good value.
  • After replacing the vent valve, the EVAP monitor may take several drive cycles to complete, so do not assume the repair failed if the light stays on immediately.

Can I keep driving with P1443?

It is generally safe to continue driving with P1443, as it primarily affects emissions and does not compromise engine performance or safety. Avoid topping off the fuel tank excessively and schedule a diagnosis soon to prevent potential fuel vapor leaks.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Subaru vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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