Fixing it involves a multi-step process:
1. Visual Inspection:
* Check the Vent Valve Solenoid: This is usually located near the fuel tank or charcoal canister (often under the vehicle). Look for any obvious damage, loose connections, or broken wires. A multimeter can check the solenoid's continuity (resistance) to confirm it works. The specifications are in your repair manual or online resources.
* Inspect the Vacuum Lines: Carefully examine all vacuum lines connected to the vent solenoid and the canister for cracks, leaks, or disconnections. Replace any damaged lines.
* Check the Charcoal Canister: Inspect the canister itself for damage. While less likely to be the direct cause of P0446, a severely damaged or clogged canister can affect the system's operation.
2. Testing the Vent Valve Solenoid:
* Ohm Test: Use a multimeter to check the resistance of the solenoid's coil. The resistance should fall within the manufacturer's specifications. A short circuit, open circuit, or resistance far outside the specifications indicates a faulty solenoid.
* Voltage Test: With the ignition on, check the voltage at the solenoid's connector. It should receive power when the PCM commands it to open. A lack of voltage indicates a wiring problem or PCM issue (less likely in this case).
* Actuation Test: If you have a scan tool that allows actuating components, attempt to command the vent valve to open and close. Listen for a click or observe the valve's movement (if accessible) to confirm functionality.
3. Repair or Replacement:
* Replace the Vent Solenoid: If testing indicates a faulty solenoid, replace it. This is often the most straightforward solution.
* Repair Vacuum Lines: Repair or replace any damaged vacuum lines.
* Replace the Charcoal Canister: If the canister is damaged or clogged, it might need to be replaced, though this is less common for this specific code.
* Wiring Repair: If you find broken or damaged wiring, repair or replace the affected sections. This requires careful tracing and potentially splicing.
Important Considerations:
* Repair Manual: A Ford Taurus repair manual is highly recommended. It will provide detailed diagrams, specifications, and troubleshooting procedures for the EVAP system.
* Scan Tool: A code reader is essential for retrieving the code and potentially performing tests. A more advanced scan tool might allow you to monitor live data from the EVAP system to better diagnose the problem.
* Safety: Fuel systems can be dangerous. Always disconnect the negative battery terminal before working on the fuel system. Work in a well-ventilated area.
If after these steps the code remains:
The problem might be more complex, involving a faulty PCM, wiring harness issue deeper within the system, or even a leak elsewhere in the EVAP system (requiring a pressure test). In such cases, seeking professional help from a mechanic is advised. A smoke test can help locate small leaks in the EVAP system.
