P0442 on 2009-2013 Infiniti FX50: EVAP Small Leak Causes and Fixes

What's Unique About the 2009-2013 Infiniti FX50

For this generation of Infiniti vehicles, the gas cap is such a common culprit for P0442 that Infiniti released a specific Technical Service Bulletin (TSB #ITB09012F) to guide technicians to check it first. This TSB explicitly states that for 2007-2011 models, a loose cap is a likely cause for P0442, P0455, or P0456. This suggests that either the original cap's seal degrades predictably or that owners frequently don't tighten it enough, making it the highest probability cause before any other part is considered. The VK50VE engine and the Nissan FM platform it's built on are generally reliable, making wear-and-tear items in the EVAP system the most probable failure points.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on
• Slight fuel odor near the rear of the vehicle (less common)
• A 'Loose Fuel Cap' warning may appear on the instrument display on some models.

Most Likely Causes

1. Loose or Improperly Installed Fuel Cap 🔴 High Probability → Shop Fuel Tank Cap This is the most common cause, as highlighted by Infiniti's own service bulletins (ITB09012F and ITB13-044J). It's easy to not tighten the cap until it clicks, breaking the EVAP system's seal. The TSBs were created specifically to address this frequent and simple-to-fix issue.
   How to confirm: Remove the fuel cap and reinstall it, ensuring you turn it until it clicks at least two to three times. Clear the code and drive for a few days. If the code does not return, this was the issue.
   Typical fix: Tighten the fuel cap correctly.
   Est. part cost: $0
2. Worn or Faulty Fuel Cap Seal 🔴 High Probability → Shop Fuel Tank Cap The rubber O-ring on the gas cap can become hard, brittle, and cracked over time, preventing a proper seal. This is a common wear item on all vehicles, including the FX50.
   How to confirm: Visually inspect the rubber seal on the gas cap for any signs of cracking, tearing, or hardening. If it looks worn, it's likely the cause. An OEM replacement is strongly recommended as aftermarket caps can have sealing issues.
   Typical fix: Replace the fuel cap with a new OEM part to ensure a perfect fit. Aftermarket caps can sometimes cause sealing issues.
   Est. part cost: $30-$55
3. Faulty EVAP Canister Purge Volume Control Solenoid Valve 🟡 Medium Probability → Shop Vapor Canister This valve, located in the engine bay, controls the flow of fuel vapors to the engine. It can get stuck partially open, creating a small leak. This is a known failure point on many Nissan and Infiniti vehicles.
   How to confirm: With the engine off and the electrical connector unplugged, the valve should be closed and not allow air to pass through. You can test this by removing the valve and trying to blow through it; if air passes, it's faulty. A professional may use a scan tool to command it open and closed while monitoring system pressure.
   Typical fix: Replacement of the purge valve. It is typically mounted on or near the engine's intake manifold.
   Est. part cost: $60-$160
4. Cracked or Disconnected EVAP Hose 🟡 Medium Probability Rubber hoses become brittle with age and exposure to engine heat, leading to small cracks. A hose could also have been disconnected during other maintenance. The most effective method to find such a leak is a smoke test.
   How to confirm: Perform a thorough visual inspection of all EVAP lines between the engine bay and the fuel tank. The most effective method is to have a professional perform a smoke test, which forces low-pressure smoke through the system to reveal the exact location of any leaks.
   Typical fix: Replace the cracked section of hose or the entire hose assembly.
   Est. part cost: $10-$50
5. Faulty EVAP Vent Control Valve (Canister Close Valve) ⚪ Low Probability → Shop Vapor Canister Vent Valve Located at the rear of the vehicle on or near the charcoal canister, this valve can fail or its O-ring seal can degrade, causing a leak. Its location exposes it to road debris and moisture, which can lead to corrosion or damage over time.
   How to confirm: The valve is normally open and closes when voltage is applied. It can be tested for functionality with a scan tool or by applying 12V power and listening for a click. A smoke test will often reveal a leak at the valve or its seal if it has failed.
   Typical fix: Replace the vent control valve and its O-ring. This often involves lowering the charcoal canister for access. On some Nissan/Infiniti platforms, owners have had success replacing the entire canister assembly which includes this valve.
   Est. part cost: $70-$150

Rare But Worth Checking

• Cracked Charcoal Canister: → Shop Vapor Canister The plastic housing of the canister itself can develop a hairline crack from road debris impact or age, creating a small leak that is difficult to find without a smoke test.
• Leaking Fuel Tank Filler Neck: → Shop Fuel Tank Rust or corrosion on the metal filler neck where the gas cap seals can create an uneven surface, preventing a proper seal and causing a P0442 code.

Diagnosis Steps

1. First, check the fuel cap. Ensure it is tightened until it clicks several times. If the cap is old or the seal appears damaged, replace it with an OEM part.
2. Clear the trouble code with an OBD-II scanner.
3. Drive the vehicle for a few days to allow the EVAP system monitor to run again. The monitor requires the fuel level to be between 1/4 and 3/4 full to run its self-test. If the code does not return, the issue is resolved.
4. If the code returns, perform a careful visual inspection of all accessible EVAP hoses and components in the engine bay and under the vehicle, near the fuel tank. Look for any obvious cracks, damage, or loose connections.
5. If no obvious issues are found, the most effective next step is a professional smoke test. This test will fill the EVAP system with visible smoke, making it easy to pinpoint the exact source of the small leak. When performing a smoke test, remember the vent valve is normally open, so it must be commanded closed with a scan tool to properly pressurize the system.
6. Based on the smoke test results, test the specific leaking component (e.g., purge valve, vent valve) for correct electrical and mechanical operation before replacing it. For example, a purge valve can be tested with a 12V source to see if it clicks and seals properly.

Parts You'll Likely Need

• Fuel Tank Cap (OEM #17251-4BA0B) — This is the most frequent cause of a P0442 code on this vehicle, as confirmed by Infiniti TSBs. The seal wears out over time.
  Trusted brands: Infiniti (OEM), Motorad
  OEM price range: $35-$55
  Aftermarket price range: $15-$30
• EVAP Canister Purge Valve (OEM #14930-JK20B) — This valve is a common failure point that can stick open, causing a constant small leak in the system.
  Trusted brands: Infiniti (OEM), Dorman, Hitachi
  OEM price range: $150-$200
  Aftermarket price range: $50-$100
• EVAP Vent Control Valve (OEM #14935-JF00B) — Located near the charcoal canister, this valve can fail due to exposure to the elements, or its O-ring seal can degrade, causing a leak. Part number 14935-JF00E is a newer, superseded version that fits many Nissan and Infiniti models.
  Trusted brands: Infiniti (OEM), Dorman
  OEM price range: $100-$140
  Aftermarket price range: $40-$80

Related Codes That Often Appear With This One

• P0455 — This code indicates a large EVAP leak. It can appear with P0442 if the gas cap is very loose or completely missing, or if a hose has become completely disconnected.
• P0456 — This code indicates a very small EVAP leak. These three codes (P0442, P0455, P0456) are a family of codes related to the size of the detected leak and are often addressed together in service bulletins.

Technical Service Bulletins (TSBs) & Recalls

• ITB09012F: States that for 2007-2011 Infiniti vehicles, a loose fuel filler cap may be the cause for P0442, P0455, or P0456 codes.
• ITB13-044J & ITB13-044g: General information bulletins for 2012 and newer Infiniti vehicles regarding EVAP leak codes P0442, P0455, and P0456, which also emphasize checking the gas cap first and provide a diagnostic flowchart.

Platform-Specific Known Issues

• High Mileage Oil Consumption: While not directly related to P0442, the VK50VE engine can consume oil at higher mileages (e.g., over 200,000 miles). One owner reported consumption of about 1 quart per 3,000 miles. This is a characteristic to be aware of during general maintenance but does not cause EVAP codes.

Mechanic-Grade Diagnostic Values

• EVAP Canister Purge Valve Resistance — expected: 20 to 30 Ohms. Failure: A reading that is too high, too low, or infinite (open circuit) indicates a faulty valve.
• EVAP Vent Control Valve Resistance — expected: 20 to 50 Ohms. Failure: An open circuit (infinite resistance) or a reading far outside the expected range indicates a bad solenoid coil.

Scan Tool Commands That Help

• Infiniti CONSULT or similar professional scanner: EVAP System Leak Check / Activation Test — This function is used to command the EVAP vent valve closed, sealing the system. This is a required step before performing a smoke test to ensure the system is properly pressurized and the smoke doesn't just exit through the normally-open vent.
• Infiniti CONSULT or similar professional scanner: Vent Valve Activation — This bidirectional command directly toggles the vent valve between 'Venting' (open) and 'Not Venting' (closed). This allows a technician to confirm the valve's solenoid is functioning electronically before physically removing it for testing.

Wiring & Ground Locations

• ECM (Engine Control Module) — Located behind the glove box on the passenger side.. The ECM controls and monitors the entire EVAP system, including the purge and vent valves. Any wiring tests for these components will ultimately lead back to the ECM connectors.
• BCM (Body Control Module) — Located in the passenger kick panel area.. The BCM is involved in various vehicle functions and shares data networks with the ECM. While not a primary cause, wiring issues near the BCM could potentially affect related systems.
• Engine Ground Wires — On the front of the engine block.. A forum post for a similar Infiniti platform noted that an improperly located ground wire on the front of the engine caused various electrical issues. While not directly linked to P0442 in the post, a poor ground for the ECM or related sensors could cause erratic behavior and false codes.
• EVAP Canister Purge Volume Control Solenoid Valve Fuse — Fuse #F34, located in the fuse block in the left front of the engine compartment.. This fuse supplies power to the purge valve. If the fuse is blown, the valve will not operate, though this would typically set a circuit code rather than a small leak code.

Real Owner Repair Stories

• Infiniti Scene forum user (Infiniti FX (similar platform)) — VDC and Slip lights on, erratic behavior.
  ❌ Tried (didn't work) Initial diagnosis was unclear.
  ✅ What actually fixed it The user had installed an aftermarket grounding wire kit. The problem was resolved by moving the ground wires from a mounting point on the plenum to a lower bolt on the front of the engine block, as recommended by the kit manufacturer for another vehicle (G35) that had a similar issue.

"I Checked Everything" — The Actual Cause

• A faulty fuel tank pressure (FTP) sensor can sometimes cause a P0442 code. The ECM relies on the FTP sensor to measure pressure changes during the EVAP self-test. If the sensor provides an inaccurate reading, the ECM may incorrectly interpret it as a small leak, even if the system is perfectly sealed and passes a smoke test.

OEM Part Supersession History

• 14935-JF00A, 14935-JF00B, 14935-JF02C → 14935-JF00E — Standard part evolution for improved reliability or manufacturing efficiency.
  Heads up: Part 14935-JF00E is the current recommended replacement for the EVAP Vent Control Valve and is widely listed as compatible with the 2009-2013 FX50 and many other Nissan/Infiniti models.