P1446 – EVAP Vacuum Solenoid Circuit Malfunction

Urgency Assessment

The P1446 code indicates a malfunction in the Evaporative Emission Control (EVAP) system, specifically related to the canister vent control valve. While this issue does not pose an immediate safety risk, it can lead to increased emissions and reduced fuel economy. Drivers can continue operating the vehicle, but should address the problem promptly to maintain optimal performance and comply with emissions regulations.

Code Description

P1446 is a manufacturer-specific code primarily associated with Nissan and Infiniti vehicles. It indicates that the Engine Control Module (ECM) has detected a malfunction in the EVAP canister vent control valve circuit or its operation. The official definition may vary slightly between manufacturers, but generally refers to the valve being stuck closed or failing to respond properly to ECM commands.

Affected Systems and Components

The P1446 code directly involves the EVAP system, which is designed to prevent fuel vapors from escaping into the atmosphere. Key components include:

1. Fuel tank
2. EVAP canister
3. Canister vent control valve
4. Purge control valve
5. Pressure sensor
6. Various hoses and lines

The canister vent control valve is the primary focus for this code. It controls the flow of outside air into the EVAP system for purging fuel vapors.

Component Functions

The EVAP canister vent control valve plays a crucial role in the system:

• It allows fresh air to enter the EVAP canister during purging operations.
• It seals the system during leak tests performed by the ECM.
• It prevents fuel vapors from escaping when the engine is off.

The valve is typically a solenoid-operated device controlled by the ECM through a duty cycle signal.

Common Causes

Several factors can trigger the P1446 code:

1. Faulty canister vent control valve
2. Blocked or restricted vent lines
3. Electrical issues (open circuit, short to ground, or power)
4. Damaged wiring harness or connectors
5. Stuck or contaminated valve mechanism
6. ECM software issues (rare)
7. Faulty ECM (very rare)

Diagnostic Procedure

Follow these steps to diagnose the P1446 code:

1. Scan for additional codes and freeze frame data.
2. Visually inspect the EVAP system components, focusing on the vent control valve and associated wiring.
3. Check for any obvious blockages in the vent lines.
4. Use a multimeter to verify proper voltage supply to the valve (typically 12V).
5. Measure the resistance of the valve solenoid (typically 20-40 ohms at 20°C/68°F).
6. Use an oscilloscope to observe the ECM control signal to the valve.
7. Perform a smoke test to check for system leaks (pressure should hold at 0.02 bar / 0.29 psi for at least 2 minutes).
8. Use a scan tool to command the valve open and closed, listening for audible clicks.
9. If possible, remove the valve and test its operation bench-side.

Solutions

Based on diagnostic results, potential fixes include:

1. Replacing the faulty canister vent control valve
2. Repairing or replacing damaged wiring
3. Clearing blockages in vent lines
4. Updating ECM software (if applicable)
5. In rare cases, replacing the ECM

Prevention

To avoid future P1446 codes:

1. Regularly inspect EVAP system components for damage or wear.
2. Avoid overfilling the fuel tank.
3. Ensure the gas cap is properly tightened after refueling.
4. Use high-quality fuel to minimize contaminants.
5. Address any fuel system or engine performance issues promptly.

Repair Costs

Estimated costs (USD/EUR):

• Diagnostic fee: $75-150 / €65-130
• Canister vent control valve replacement: $150-300 / €130-260
• Wiring repair: $100-200 / €85-175
• ECM software update: $100-150 / €85-130

Labor rates and part prices may vary by region and vehicle model.

DIY Repair Guide

For skilled mechanics:

1. Locate the canister vent control valve (typically near the EVAP canister).
2. Disconnect the battery negative terminal.
3. Unplug the electrical connector from the valve.
4. Remove any mounting bolts or clips securing the valve.
5. Carefully remove the valve, noting its orientation.
6. Install the new valve in the same orientation.
7. Reconnect the electrical connector and secure the valve.
8. Reconnect the battery and clear the code.
9. Perform a smoke test to ensure proper sealing.
10. Test drive the vehicle and monitor for code recurrence.

Related Issues

P1446 may be accompanied by:

• P0440-P0457 (various EVAP system codes)
• P0171/P0174 (system too lean codes)
• Difficulty refueling or "clicking" from the fuel nozzle

Vehicle Specifics

While P1446 is primarily associated with Nissan and Infiniti vehicles, similar codes (e.g., P0446) may appear on other makes. The exact location and design of the canister vent control valve can vary between models. Always consult the specific vehicle's service manual for precise diagnostic and repair procedures.

Frequently Asked Questions About P1446

What does the P1446 code mean?

P1446 indicates an Evaporative Emission Control (EVAP) System Vent Control Valve malfunction, specifically that the valve is stuck closed or not responding properly to ECM commands.

Is it safe to drive with a P1446 code?

While not immediately dangerous, it’s best to address the issue promptly to maintain optimal performance and emissions control. You can continue driving, but should have it checked soon.

What causes a P1446 code?

Common causes include a faulty vent control valve, blocked vent lines, electrical issues, damaged wiring, or rarely, ECM problems.

How do I diagnose a P1446 code?

Start with a visual inspection of EVAP components, check for blockages, use a multimeter to test voltage and resistance, and perform a smoke test to check for leaks.

Can a loose gas cap cause P1446?

While a loose gas cap can cause some EVAP codes, it’s unlikely to be the sole cause of P1446, which specifically relates to the vent control valve.

How do I locate the EVAP canister vent control valve?

It’s typically located near the EVAP canister, often behind the left rear wheel or near the fuel tank.

What are the symptoms of a P1446 code?

You may notice decreased fuel economy, difficulty refueling, or simply the check engine light.

How much does it cost to fix a P1446 code?

Repair costs can range from $150-$300 for parts and labor, depending on the specific issue and vehicle model.

Can I clear the P1446 code myself?

You can clear it using an OBD-II scanner, but it will return if the underlying issue isn’t fixed.

Is P1446 a manufacturer-specific code?

Yes, it’s primarily associated with Nissan and Infiniti vehicles, though similar issues may trigger different codes in other makes.

How often should the EVAP canister vent control valve be replaced?

There’s no set interval; replace it only when it fails or as part of diagnosing EVAP system issues.

Can a P1446 code affect my vehicle’s emissions test?

Yes, it can cause your vehicle to fail an emissions test as it indicates a problem with the emissions control system.

What’s the difference between P1446 and P0446?

P1446 is a manufacturer-specific code, while P0446 is a generic OBD-II code. Both relate to EVAP system vent control issues.

Can cold weather cause a P1446 code?

Extreme cold can sometimes affect EVAP system operation, but it’s not a common cause of P1446.

How long does it take to replace an EVAP canister vent control valve?

An experienced mechanic can typically complete the replacement in 1-2 hours.

Can I drive long distances with a P1446 code?

While possible, it’s not recommended as it may lead to decreased fuel efficiency and potential damage to other EVAP system components.

Will a P1446 code clear itself?

It’s unlikely to clear on its own unless it was triggered by a temporary condition, which is rare for this specific code.

Can a faulty O2 sensor cause a P1446 code?

While O2 sensors can cause various engine codes, they are not directly related to P1446, which is specific to the EVAP system.

Is there a way to prevent P1446 from occurring?

Regular maintenance of your vehicle’s EVAP system, including visual inspections and prompt addressing of any fuel system issues, can help prevent P1446.

Can aftermarket modifications cause a P1446 code?

Modifications that affect the fuel system or EVAP system could potentially trigger P1446, especially if they interfere with the vent control valve operation.