What is OBD-II Code P14A6 in an Infiniti?
OBD-II diagnostic trouble code P14A6 is a manufacturer-specific code primarily used by Nissan and its luxury division, Infiniti. This code indicates a fault within the Evaporative Emission Control (EVAP) system, specifically pointing to a “Small Leak Detected.” Unlike generic EVAP codes (like P0442), P14A6 is tailored to the sophisticated monitoring strategies of modern Infiniti vehicles, such as the Q50, Q60, QX50, QX60, and their predecessors like the G37. The system’s primary goal is to prevent fuel vapors from escaping into the atmosphere by storing them in a charcoal canister and later purging them into the engine to be burned. Code P14A6 is set when the Engine Control Module (ECM) detects a leak smaller than the specification for a “gross leak” but larger than the system’s tightness threshold, typically equivalent to a hole of about 0.020 inches (0.5mm) in diameter.
Primary Causes of the P14A6 Code in Infiniti Models
Pinpointing the exact source of a small EVAP leak requires a systematic approach. The leak can occur anywhere in the sealed network of hoses, valves, and components that manage fuel vapor.
1. Faulty or Loose Gas Cap
This is the most common and easily remedied cause. A cracked, worn, or improperly tightened gas cap fails to seal the fuel filler neck, allowing vapors to escape. Always start diagnostics by inspecting the cap.
2. Leaking or Degraded EVAP Hoses and Lines
The plastic and rubber hoses that connect the EVAP canister, purge valve, vent valve, and fuel tank can become brittle, cracked, or disconnected over time, especially near heat sources or areas prone to road debris impact.
3. Malfunctioning EVAP Canister Vent Control Valve
This valve, often located near the EVAP canister, controls the flow of fresh air into the canister and seals the system during leak tests. If it sticks open or fails to seal, it will cause a P14A6 code.
4. Defective Fuel Tank Pressure Sensor (FTPS)
This sensor monitors pressure/vacuum changes within the fuel tank during the EVAP system self-test. A sensor providing inaccurate data can trick the ECM into thinking a leak is present when the system is actually sealed.
5. Faulty EVAP Canister Purge Valve
While often associated with purge flow codes, a purge valve that is stuck slightly open can also contribute to a small leak condition, as it may not hold vacuum properly.
Symptoms and Diagnostic Procedure for P14A6
Unlike some engine codes, P14A6 may not cause obvious drivability issues, but it will trigger specific warnings and can lead to failed emissions inspections.
Common Symptoms
- Illuminated Check Engine Light (MIL): The primary and often only immediate symptom.
- Possible Fuel Odor: A faint smell of gasoline may be noticeable near the vehicle if the leak is significant enough.
- Failed Emissions Test: The vehicle will not pass state or local emissions inspections with an active EVAP leak code.
- No Performance Issues: The engine typically runs normally, as this is an emissions-related fault, not a combustion fault.
Step-by-Step Diagnostic Approach
A proper diagnosis moves from the simplest checks to more complex tests. You will need a professional-grade OBD2 scanner capable of commanding EVAP system components and viewing live data.
- Step 1: Visual Inspection: Check the gas cap for damage and ensure it clicks at least three times when tightened. Inspect all visible EVAP lines from the fuel tank to the engine bay for cracks, disconnections, or damage.
- Step 2: Clear Code and Monitor: Clear the DTC with your scanner. Drive the vehicle through multiple drive cycles. If the code returns quickly, the leak is likely persistent. If it takes many cycles, it may be intermittent.
- Step 3: Smoke Machine Test (Most Effective): This is the industry-standard method. A smoke machine introduces non-toxic smoke under low pressure into the EVAP system. Any leak will be revealed by smoke escaping from the source (e.g., a hose, valve, or even a porous fuel tank).
- Step 4: Component Testing: Use your scanner’s bi-directional controls to command the Vent Control Valve and Purge Valve open/closed while listening for audible clicks. Check the FTPS live data for plausible readings (should change when the gas cap is loosened).
Repair Solutions and Estimated Costs for P14A6
The repair cost varies dramatically based on the root cause. DIY repairs are possible for simpler issues, while others require professional tools and expertise.
Common Repairs and Parts
- Replace Gas Cap: Cost: $20 – $50. The simplest fix.
- Replace EVAP Vent Control Valve: Cost: Part $80 – $200, Labor 0.5-1 hour. Common on many Infiniti models.
- Replace EVAP Hoses or Lines: Cost: Part $30 – $150 per hose, Labor varies. Requires locating the specific leaking hose.
- Replace Fuel Tank Pressure Sensor: Cost: Part $60 – $150, Labor 0.5-1.5 hours. Often accessed under the vehicle near the fuel tank.
- Replace EVAP Canister: Cost: Part $150 – $400, Labor 1-2 hours. Necessary if the canister itself is cracked or the internal valve is faulty.
Professional vs. DIY Repair
For a skilled DIYer with a smoke machine, fixing a P14A6 code can be straightforward once the leak is found. However, without a smoke machine, diagnosis becomes guesswork. A professional shop will typically charge 1-2 hours of diagnostic time ($100-$250) plus parts and labor for the repair. Total bills often range from $150 for a simple gas cap fix to $600+ for a canister or complex leak repair.
Preventative Maintenance and Conclusion
Preventing P14A6 and other EVAP codes revolves around simple habits and awareness. Always tighten your gas cap securely until it clicks multiple times. During routine service, ask your technician to inspect visible EVAP lines, especially in regions with harsh winters or where rodents are a concern. Addressing a small leak promptly prevents it from worsening and ensures your Infiniti remains environmentally compliant and ready to pass any emissions test. While code P14A6 is not an emergency that will strand you, it is a clear signal from your vehicle’s sophisticated monitoring system that the sealed EVAP system integrity has been compromised and requires attention.