P0456 on 2007-2012 Infiniti FX35: Causes and Fixes for a Small EVAP Leak

What's Unique About the 2007-2012 Infiniti FX35

The 2007-2012 Infiniti FX35 spans two vehicle generations (S50 and S51), but the common causes for P0456 are consistent across both. Infiniti and Nissan have issued multiple Technical Service Bulletins (TSBs) that are highly relevant to this code across their lineups. TSB ITB09012F directly points to a loose fuel cap as a primary cause for the 2007-2011 models. Furthermore, a series of TSBs, most notably ITB17-042, identifies a failing O-ring on the EVAP vent control valve as a very common source of this specific leak code on many Infiniti models, including the S51 FX35. Initially, these TSBs recommended replacing only the O-ring, but later versions like ITB17-042D (from March 2021) updated the procedure to replace the entire vent control valve assembly, as the O-ring is no longer sold as a separate service part by the dealer.

Diagnostic Flowchart

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

Generation note: This guide covers the late first-generation (S50, 2007-2008) and early second-generation (S51, 2009-2012) Infiniti FX35. While parts may differ slightly, the diagnostic process and common failure points for code P0456 are largely the same for both generations. The S51 is explicitly mentioned in TSBs regarding the common vent valve O-ring failure.

Symptoms You May Notice

• Check Engine Light is on
• A faint smell of gasoline, possibly near the rear of the vehicle.
• Potentially a "LOOSE FUEL CAP" warning on the dashboard for some models.
• Loss of the typical 'hiss' sound when opening the gas cap, indicating the system is not holding pressure.

Most Likely Causes

1. Loose or Faulty Gas Cap 🔴 High Probability → Shop Fuel Tank Cap This is the most common cause for P0456 on any vehicle and is specifically cited by Infiniti 🎬 Watch: A quick DIY fix for the P0456 code. in TSB ITB09012F for the 2007-2011 models. Forum users consistently report this as the first step, and many modern Infinitis will display a specific 'Loose Fuel Cap' message before the Check Engine Light appears.
   How to confirm: Ensure the gas cap is tightened until it clicks several times. Inspect the cap's O-ring or seal for cracks, stiffness, or damage. If the seal is compromised, the cap cannot hold pressure.
   Typical fix: Tighten the existing cap, clear the code, and drive for a few days. If the code returns, replace the gas cap with a new OEM part, as aftermarket caps can sometimes cause sealing issues.
   Est. part cost: $25-$40
2. Failing EVAP Canister Vent Control Valve or O-Ring 🔴 High Probability → Shop Vapor Canister Vent Valve Infiniti TSB ITB17-042b and its successors specifically identify a leak at the vent control valve O-ring as a common cause for P0456. The valve is exposed to the elements under the car near the rear passenger wheel, and the solenoid or its seal can fail over time. This is the most likely culprit if the gas cap is not the issue.
   How to confirm: The valve is located near the charcoal canister at the rear of the vehicle, on the passenger side. A visual inspection may not be sufficient. The best way to confirm is with a smoke test, which will show smoke leaking from the valve body or where it seals against the canister. A technician can also command the valve closed with a scan tool to see if it holds pressure.
   Typical fix: Initially, Infiniti recommended replacing just the O-ring (Part # 16618-JF00A). However, TSB ITB17-042D (March 2021) states the O-ring is no longer sold separately and the official repair is to replace the entire vent control valve assembly. 🎬 Watch: Step-by-step guide to replacing the vent control valve. This involves removing a protective shield (which may have rusted bolts), disconnecting the electrical connector and hoses, and twisting the valve to remove it from the canister.
   Est. part cost: $65-$120
3. Cracked or Disconnected EVAP Hoses 🟡 Medium Probability Rubber hoses become brittle and crack with age and exposure to heat cycles. A tiny crack in any of the vapor lines connecting the fuel tank, charcoal canister, and purge valve can cause this code. In some cases, a hose clamp may be missing or loose from a previous repair.
   How to confirm: Visually inspect all accessible EVAP hoses for obvious cracks, splits, or loose connections. A smoke test is the most effective method to find a small hose leak that isn't visible.
   Typical fix: Replace the damaged section of hose. Ensure clamps are secure.
   Est. part cost: $10-$50
4. Faulty EVAP Purge Valve/Solenoid ⚪ Low Probability → Shop Vapor Canister While less common for a small leak code, the purge valve can fail by not closing completely, creating a constant small leak path. It is located in the engine bay, making it easier to access than the vent valve.
   How to confirm: The purge valve is typically located in the engine bay, on or near the intake manifold. With the engine off, it should be closed. You can test it by removing it and trying to blow through it; if air passes, it's faulty. A technician can also command it with a scan tool to check for function and leaks.
   Typical fix: Replace the purge valve assembly.
   Est. part cost: $150-$200

Rare But Worth Checking

• Cracked EVAP Charcoal Canister: → Shop Vapor Canister The canister itself can develop hairline cracks from road debris impact or age, causing a small leak. This is usually diagnosed with a smoke test after all other common components have been checked. Overfilling the gas tank repeatedly can also saturate the canister with liquid fuel, causing damage.
• Leaking Fuel Tank Pressure Sensor: → Shop Fuel Tank The sensor that monitors the system pressure can itself develop a leak in its seal, though this is uncommon. If the sensor fails electrically, it will usually set a different code.
• Rusted Fuel Filler Neck or Vent Lines: → Shop Fuel Filler Neck In areas with heavy road salt use, the metal fuel filler neck or the adjacent EVAP vent lines can rust through, creating a leak. One owner on a G35Driver forum reported this was the ultimate cause of their P0456 after replacing the gas cap and vent valve. This can be hard to spot and often requires a smoke test to pinpoint.

Diagnosis Steps

1. Check the gas cap. Remove it, inspect the seal for damage, and retighten it until it clicks multiple times. Clear the code and see if it returns after a few days of driving.
2. If the code returns, perform a thorough visual inspection of all accessible EVAP hoses and lines, from the engine bay to the rear of the vehicle, looking for cracks or loose clamps.
3. Locate the EVAP canister and vent control valve at the rear passenger side of the vehicle. Inspect the valve and its connection to the canister for any obvious damage. Be aware that the protective shield bolts are prone to rusting.
4. The most effective diagnostic step is to perform a smoke test. This involves injecting low-pressure smoke into the EVAP system's service port. The leak will be revealed by the escaping smoke.
5. If smoke emerges from the gas cap, it's faulty.
6. If smoke emerges from the vent control valve body or its seal, the valve assembly needs replacement, per the latest TSBs.
7. If smoke emerges from a hose or the canister itself, that component is the source of the leak.
8. If smoke emerges from the area around the fuel filler pipe, inspect the metal lines for rust perforation.

Parts You'll Likely Need

• Fuel Filler Cap (OEM #17251-JK60D) — This is the most frequent and simplest cause of a P0456 code, as confirmed by TSB ITB09012F. It is always the first recommended replacement.
  Trusted brands: Genuine Infiniti, Stant
  OEM price range: $30-$40
  Aftermarket price range: $15-$25
• EVAP Canister Vent Control Valve (OEM #14935-JF00E) — This valve or its O-ring seal is the second most common failure point, as documented in a series of Infiniti TSBs (ITB17-042). The latest TSBs recommend replacing the entire valve assembly. Part number 14935-JF00E is a superseding part for earlier versions like 14935-AM60B, 14935-JF00A/B/C/D.
  Trusted brands: Genuine Nissan/Infiniti, Hitachi, Dorman, Standard Motor Products
  OEM price range: $65-$120
  Aftermarket price range: $50-$90

Related Codes That Often Appear With This One

• P0442 — P0442 indicates a 'small leak,' while P0456 indicates a 'very small leak.' They point to the same type of problem, just differing in the detected leak size. It's common to see either code for the same root cause, and service manuals often instruct diagnosing P0456 first if both are present.
• P0455 — P0455 indicates a 'large leak.' If you see this with P0456, it could mean an intermittent issue, such as a gas cap that was left very loose once, triggering P0455, and now has a smaller, more persistent seal problem causing P0456.

Technical Service Bulletins (TSBs) & Recalls

• ITB17-042b / ITB17-042c / ITB17-042D: 'DTC P0456 CAUSED BY EVAP LEAK AT VENT CONTROL VALVE O-RING'. This series of bulletins is the most critical for this issue. It confirms the O-ring as the leak source. The latest versions instruct replacing the entire valve assembly.
• ITB09012F: 'SERVICE INFORMATION'. Specifically calls out a loose fuel fill cap as a potential cause for P0456 on 2007-2011 Infiniti vehicles.
• ITB13-044J: 'EVAP LEAK DTC P0442, P0455, P0456 INFORMATION'. A general bulletin advising technicians to always check for a loose fuel cap first before proceeding with more complex diagnostics.
• NTB17-082b: The parallel TSB for Nissan vehicles, confirming the vent valve O-ring issue is widespread across the brand family, applying to all 2008+ Nissan models.

Platform-Specific Known Issues

• Infiniti TSB ITB09012F explicitly states that a loose fuel fill cap may be the cause for P0456 on 2007-2011 models.
• Infiniti TSB ITB17-042b was issued for numerous models, including the S51 FX35, for P0456 caused by a leak at the vent control valve O-ring. This makes the vent valve a high-probability suspect if the gas cap is not the issue.
• Later TSB ITB17-042D updated the repair procedure, stating the O-ring (16618-JF00A) is no longer available separately and the entire vent control valve assembly must be replaced.

Mechanic-Grade Diagnostic Values

• EVAP Canister Purge Volume Control Solenoid Valve Power Supply — expected: Battery voltage (>11V). Failure: No voltage indicates a problem with the power supply circuit, potentially a blown fuse or wiring issue.
• EVAP Canister Purge Volume Control Solenoid Valve Circuit Continuity — expected: Continuity should exist between the solenoid valve's harness connector and the corresponding pins at the ECM connector.. Failure: No continuity (an open circuit) or the presence of a short to ground or power in the harness.

Scan Tool Commands That Help

• CONSULT-III plus (C-III plus): Active Test: Close Vent Control Valve — This command is used to manually close the EVAP canister vent control valve, sealing the system. It is a critical step when using the scan tool to perform a leak check or when preparing to use a smoke machine, as it confirms if the valve is responding to commands.

Wiring & Ground Locations

• EVAP Canister Vent Control Valve (B253) — Under the right rear of the vehicle, mounted to the charcoal canister.. This is the physical location of the most common failure part (after the gas cap) for code P0456. Knowing its location is essential for inspection and replacement.
• EVAP Canister Purge Volume Control Solenoid Valve — In the engine compartment. On the 3.5L VQ35HR, it is located near the rear of the engine.. This is the location of the secondary valve in the EVAP system. While a less common cause for P0456, it must be located for testing if other components check out.
• Fuse #10 (IPDM E/R) — In the IPDM E/R (Intelligent Power Distribution Module Engine Room), which is the main fuse and relay box in the engine compartment.. This 15A fuse supplies power to both the EVAP Canister Vent Control Valve and the EVAP Canister Purge Volume Control Solenoid Valve. If this fuse is blown, neither valve will operate, leading to EVAP system codes.

Real Owner Repair Stories

• G35Driver Forum User (Infiniti G35 (shares similar platform and EVAP components)) — Persistent P0456 code after filling up with gas.
  ❌ Tried (didn't work) Replacing the gas cap., Checking for obvious hose leaks.
  ✅ What actually fixed it The owner discovered the metal fuel filler neck was badly rusted. The corrosion prevented the new gas cap from creating a perfect seal, causing the small leak. Replacing or repairing the rusted filler neck resolved the issue.

"I Checked Everything" — The Actual Cause

• In some cases, a vehicle can pass a smoke test (showing no visible leaks) but still set a P0456 code. This can happen if the Fuel Tank Pressure (FTP) sensor is faulty and providing incorrect readings to the computer. The sensor may make the ECM believe a leak exists when the system is actually sealed, leading to a false code after all physical components have been verified as good.

OEM Part Supersession History

• 14935-AM60B, 14935-JF00A, 14935-JF00B, 14935-JF00C, 14935-JF00D → 14935-JF00E, and most recently 14935-JF02C — Part has been updated multiple times by the manufacturer to improve reliability and address failures.
  Heads up: The latest part number (14935-JF02C) is the recommended replacement for all previous versions. While older stock may be available, using the newest revision is advised.

Model Year Variations Within This Range

• 2009-2012 (S51 Generation): The component location identifiers (e.g., B253 for the vent valve) and fuse box layouts cited from wiring diagrams are specific to the S51 generation. While the physical location of the parts is the same as the S50 (2007-2008), the service manual references will be different.
• 2007-2011: Technical Service Bulletin ITB09012F, which specifically calls out a loose fuel fill cap as a primary cause for P0456, officially applies to models up to 2011. [NHTSA TSB ITB09012F]