Understanding the Infiniti P1446 Trouble Code
The OBD2 trouble code P1446 is a manufacturer-specific diagnostic code primarily associated with Infiniti and Nissan vehicles. This code indicates a malfunction within the Evaporative Emission Control (EVAP) system, specifically related to the “EVAP Canister Closed Valve Function.” When this code appears, it signifies that the vehicle’s Powertrain Control Module (PCM) has detected an irregularity in the operation of the canister closed valve, a critical component responsible for managing fuel vapor emissions.
What is the EVAP System?
The Evaporative Emission Control system is designed to prevent fuel vapors from the gas tank from escaping into the atmosphere. It captures these vapors in a charcoal-filled canister and later purges them into the engine intake to be burned during normal combustion. This system is crucial for reducing hydrocarbon emissions and meeting environmental regulations. A failure in any part of this system, as indicated by code P1446, can lead to increased emissions and potential drivability issues.
Technical Definition of P1446
According to official service manuals, P1446 is defined as “EVAP Canister Closed Valve Function.” This valve, also known as the vent control valve or purge volume control valve, is typically located on or near the charcoal canister. Its primary function is to seal the EVAP system from the atmosphere during certain operational modes, allowing the PCM to perform leak tests and control vapor flow. When the PCM detects that the valve is not responding correctly to commanded states (open or closed), it will set code P1446 and illuminate the check engine light.
Vehicles Commonly Affected by P1446
While this code is specific to Infiniti and Nissan, it has been documented across numerous models and years. The most commonly affected vehicles include:
- Infiniti G35 (2003-2006)
- Infiniti G37 (2008-2013)
- Infiniti Q50 (2014-2016)
- Infiniti FX35/FX45 (2003-2008)
- Infiniti M35/M45 (2006-2010)
- Nissan 350Z (2003-2006)
- Nissan Altima (2002-2006 with specific engines)
Symptoms and Causes of P1446 in Infiniti Vehicles
Recognizing the symptoms and understanding the potential causes of code P1446 is essential for effective diagnosis and repair. While this code doesn’t typically cause immediate drivability problems, ignoring it can lead to more significant issues over time.
Common Symptoms of P1446
Drivers may notice several indicators when the P1446 code is present, though some vehicles may show no obvious symptoms beyond the check engine light. The most frequently reported symptoms include:
- Illuminated Check Engine Light (MIL)
- Failed emissions test
- Possible fuel odor near the vehicle
- Slightly reduced fuel economy in some cases
- Rough idle in severe cases
- Other EVAP-related codes stored alongside P1446
Primary Causes of P1446
The P1446 code can be triggered by several different issues within the EVAP system. Understanding these potential causes will help streamline the diagnostic process. The most common culprits include:
- Faulty EVAP canister closed valve/vent control valve
- Damaged or corroded electrical connectors at the valve
- Broken, cracked, or disconnected vacuum hoses
- Wiring issues (open circuits, short circuits, high resistance)
- Failed charcoal canister (contaminated or damaged)
- Software issues or PCM programming faults (less common)
- Physical damage to EVAP system components from road debris
Secondary System Impacts
While the P1446 code specifically points to the canister closed valve, it’s important to consider how other system components might be affected. A malfunctioning valve can impact overall EVAP system performance, potentially causing:
- Inability to properly purge fuel vapors
- Increased pressure/vacuum in the fuel system
- Potential damage to other EVAP components over time
- Triggering of additional diagnostic trouble codes
Step-by-Step Diagnostic Procedure for P1446
Proper diagnosis of the P1446 code requires a systematic approach using appropriate tools and following manufacturer-recommended procedures. This comprehensive diagnostic guide will help identify the root cause efficiently.
Required Tools and Safety Precautions
Before beginning diagnosis, ensure you have the necessary equipment and observe important safety measures. Required tools include:
- Professional OBD2 scanner with manufacturer-specific capabilities
- Digital Multimeter (DMM) with resistance and voltage testing
- Hand vacuum pump and gauge
- Basic hand tools (sockets, screwdrivers, pliers)
- Vehicle service manual or repair database access
- Safety glasses and gloves
Always work in a well-ventilated area, disconnect the battery when working with electrical components, and relieve fuel system pressure before disconnecting any fuel or EVAP lines.
Visual Inspection and Preliminary Checks
Begin with a thorough visual inspection, as many EVAP system issues can be identified through careful observation. Follow these steps:
- Inspect all EVAP system hoses for cracks, brittleness, or disconnections
- Check the charcoal canister for physical damage or contamination
- Examine electrical connectors at the canister closed valve for corrosion or damage
- Verify the gas cap is properly sealed and in good condition
- Look for any obvious wiring damage or chafing in the EVAP system circuit
- Check for aftermarket modifications that might affect the EVAP system
Electrical Circuit Testing
If visual inspection reveals no obvious issues, proceed with electrical testing of the canister closed valve circuit. Follow this procedure:
- Disconnect the electrical connector from the canister closed valve
- With the key in ON position (engine off), check for battery voltage at the power supply wire using a multimeter
- Check ground circuit continuity by measuring resistance between the ground terminal and a known good ground
- Test valve resistance by measuring across the valve terminals (compare to manufacturer specifications, typically 20-40 ohms)
- Inspect for short circuits to ground or power in the control circuit
- Check for proper PCM control signal using an oscilloscope or duty cycle meter if available
Mechanical Function Testing
After verifying the electrical circuit is functioning properly, test the mechanical operation of the canister closed valve. Use these methods:
- Apply battery voltage directly to the valve terminals to verify it opens and closes (audible click should be heard)
- Use a hand vacuum pump to test valve operation under vacuum conditions
- Check for proper airflow through the valve in both open and closed states
- Test for internal leaks by applying vacuum to one port and checking if it holds
- Compare operation to known good valve if available
Repair Procedures and Prevention Strategies
Once the faulty component has been identified through systematic diagnosis, proper repair procedures must be followed to ensure a permanent fix. Additionally, understanding prevention strategies can help avoid recurrence of the P1446 code.
Component Replacement Guidelines
When replacing the EVAP canister closed valve or related components, follow these important guidelines:
- Always use OEM or high-quality replacement parts specifically designed for your Infiniti model
- Replace any damaged hoses or connectors during the repair process
- Ensure proper orientation and installation of the valve according to service manual specifications
- Clear all diagnostic trouble codes after repairs are complete
- Perform a complete EVAP system monitor drive cycle to verify proper operation
- Confirm repair success by ensuring the check engine light remains off and no codes return
Cost Considerations and Professional Assistance
Repair costs for P1446 can vary significantly depending on the root cause and whether you perform the repair yourself or seek professional help. Typical costs include:
- EVAP canister closed valve: $80-$200 for the part
- Charcoal canister: $150-$400 if replacement is necessary
- Professional labor: 1-2 hours at $80-$150 per hour
- Diagnostic fees: $50-$100 if performed by a shop
For complex electrical issues or if you’re uncomfortable with the diagnostic process, seeking professional assistance from a qualified technician with Infiniti/Nissan experience is recommended.
Preventive Maintenance Tips
While some EVAP system failures are unavoidable, proper maintenance can reduce the likelihood of P1446 and related codes. Implement these preventive measures:
- Always tighten the gas cap securely until it clicks three times
- Replace the gas cap according to manufacturer recommendations (typically every 50,000 miles)
- Avoid overfilling the gas tank beyond the automatic shutoff
- Keep the area around the charcoal canister clean and free of debris
- Address any other EVAP-related codes promptly to prevent system strain
- Have the EVAP system inspected during routine maintenance if you frequently drive in harsh conditions
Successfully diagnosing and repairing a P1446 code requires patience, proper tools, and methodical troubleshooting. By following this comprehensive guide, you can effectively address this common Infiniti EVAP system issue and restore your vehicle to proper operating condition while maintaining emissions compliance.