Infiniti G35 P0456 Code Guide (2007-2008): Causes and Fixes for a Very Small EVAP Leak

What's Unique About the 2007-2008 Infiniti G35

While any car can get this code from a loose gas cap, the 2007-2008 G35 (V36) platform is uniquely prone to a specific failure point. Infiniti issued multiple Technical Service Bulletins (TSBs) identifying that the O-ring sealing the EVAP vent control valve to the charcoal canister frequently degrades and causes this exact code. This makes the vent valve area the most probable cause after the gas cap has been ruled out, a detail specific to this and other Infiniti/Nissan models of the era sharing the FM platform.

Diagnostic Flowchart

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

Generation note: The 2007-2008 model years cover two different G35 generations. The 2007-2008 G35 Sedan is the V36 platform, while the 2007 G35 Coupe is the older V35 platform (the coupe was replaced by the G37 in 2008). The key TSBs specifically list the V36 sedan, but the EVAP system components and common failures are highly similar across both platforms and their VQ-series engines. The physical mounting of the vent control valve may differ slightly; on the V35 it is often on a bracket near the canister, while on the V36 it is typically mounted directly to the canister.

Symptoms You May Notice

• Check Engine Light (Service Engine Soon light) is on
• A 'Loose Fuel Cap' warning message may appear on the information display before the Check Engine Light turns on.
• A faint fuel smell near the rear of the car is possible, but not common. Some owners on my350z.com have noted a fuel smell when the tank is full, which accompanied the code.
• In rare cases, some owners have reported perceived performance loss when the code is active, though this is not a typical symptom.

Most Likely Causes

1. Loose or Faulty Gas Cap 🔴 High Probability This is the most common cause on all vehicles. The rubber seal on the cap can wear out, or the cap may not have been tightened properly after refueling. Many owners in forums strongly recommend using only a genuine OEM Infiniti cap, as aftermarket caps are known to cause sealing issues.
   How to confirm: Remove the gas cap and inspect the rubber seal for cracks or brittleness. Reinstall it and turn it until it clicks several times. Clear the code and drive for a few days to see if it returns. The EVAP self-test may take several drive cycles to complete.
   Typical fix: Replace the fuel filler cap. It is highly recommended to use a genuine OEM Infiniti cap (Part No. 17251-JK60D) as aftermarket caps are known to cause sealing issues.
   Est. part cost: $25-$40
2. Failing EVAP Canister Vent Control Valve or O-Ring 🔴 High Probability Infiniti issued multiple TSBs (including ITB17-042E) specifically for this problem on the 2007-2008 G35 Sedan. The O-ring that seals the valve to the canister degrades over time from exposure to elements under the car, causing a small leak. The valve is located on the charcoal canister at the rear of the vehicle, near the rear axle.
   How to confirm: A professional smoke test is the best method. Smoke is injected into the EVAP system, and the technician will watch for it to escape from the vent valve area. A technician can also use a capable scan tool to command the valve closed and monitor system pressure. The valve's solenoid coil should have a resistance of approximately 15-16 Ohms.
   Typical fix: Replace the EVAP vent control valve assembly. While older TSBs (like ITB17-042b) advised replacing only the O-ring (P/N 16618-JF00A), the most recent bulletin (ITB17-042D) states the O-ring is no longer sold separately and the entire valve assembly should be replaced.
   Est. part cost: $80-$150
3. Cracked or Disconnected EVAP Hoses 🟡 Medium Probability Rubber hoses become brittle and crack with age and exposure to heat cycles and the elements. The many connections in the EVAP system provide multiple potential failure points, especially at connection points where hoses can split.
   How to confirm: A visual inspection may reveal obvious cracks or loose connections. A smoke test is the most reliable way to find small, hard-to-see leaks in the hose lines.
   Typical fix: Replace the specific section of cracked hose. This can be a simple DIY fix if the hose is accessible.
   Est. part cost: $10-$50

Rare But Worth Checking

• Faulty EVAP Canister Purge Valve/Solenoid: This valve is located in the engine bay and controls the flow of vapors to the engine. If it fails by sticking slightly open, it can create a leak path. While less common for this code than the rear vent valve, it's a known failure point.
• Cracked Charcoal Canister: The plastic body of the canister itself can develop hairline cracks. This is usually found during a smoke test and is a more expensive repair.
• Cracked Nipple on Fuel Pump or Canister Assembly: A forum user on G35Driver reported that a small white plastic nipple for a hose on the canister was broken, causing a persistent P0456. The owner was able to replace just the nipple for a few dollars from the dealer. Another user on the same forum had a similar issue with a cracked nipple on the in-tank fuel pump assembly, which required dropping the fuel tank to repair.
• Rusted Fuel Vent/Filler Neck Line: One owner on MyG37.com with a persistent P0456 code discovered a rusted-out fuel vent return line located near the gas filler tube. This is more likely in regions that use road salt. Another user on G35Driver mentioned their gas tank filler neck was rusting badly, suspecting it as the cause.

Diagnosis Steps

1. Check the Gas Cap: Ensure it is tight by turning it until it clicks multiple times. Inspect the cap's seal for any cracks or damage. If it looks worn, replace it with an OEM cap.
2. Clear the Code: Use an OBD-II scanner to clear the P0456 code.
3. Drive the Vehicle: Drive for several days to allow the car's computer to re-run the EVAP system self-test. This may require multiple drive cycles and overnight cool-downs. If the Check Engine Light does not return, the gas cap was the likely issue.
4. Visual Inspection: If the light returns, visually inspect all accessible EVAP hoses and lines between the engine bay and the rear charcoal canister for obvious cracks, damage, or disconnections.
5. Perform a Smoke Test: This is the most effective step. A mechanic will connect a smoke machine to the EVAP service port. The machine fills the system with a harmless, visible smoke under low pressure. Any leaks will be revealed by smoke escaping from 🎬 See how a smoke test identifies small EVAP system leaks. the faulty component. Pay close attention to the vent control valve on the charcoal canister, as this is the most likely leak source per Infiniti TSBs.

Parts You'll Likely Need

• Fuel Filler Cap (OEM #17251-JK60D) — This is the most frequent and simplest cause of P0456. The seal wears out over time, and using a genuine OEM part is critical for a proper seal, as confirmed by numerous owner reports and TSB ITB09012F.
  Trusted brands: Genuine Infiniti/Nissan
  OEM price range: $25-$40
  Aftermarket price range: $15-$30
• EVAP Canister Vent Control Valve (OEM #14935-JF00E) — This is the second most common failure, specifically identified in Infiniti TSBs. The O-ring seal fails, and current service procedure is to replace the entire valve assembly. 🎬 Watch: Step-by-step guide to replacing the canister vent valve. Part number has been superseded multiple times from 14935-AM60A/B to 14935-JF00A/B/C/E.
  Trusted brands: Hitachi (often the OEM supplier), Dorman (911-503), Standard Motor Products, Genuine Infiniti/Nissan
  OEM price range: $100-$150
  Aftermarket price range: $70-$110

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 in the EVAP system, and a leak can sometimes be borderline between the two thresholds or worsen over time.
• P0455 — P0455 indicates a 'gross leak'. This code can appear with P0456 if a very small leak suddenly becomes much larger, such as a hose completely disconnecting or leaving the gas cap off entirely.

Technical Service Bulletins (TSBs) & Recalls

• ITB17-042E: 'DTC P0456 CAUSED BY EVAP LEAK AT VENT CONTROL

Platform-Specific Known Issues

• Infiniti Technical Service Bulletin ITB17-042E (and its predecessors like ITB17-042b/c/d) directly addresses DTC P0456 on the 2007-2008 G35 Sedan. It confirms the cause is often an EVAP leak at the vent control valve O-ring.
• While earlier versions of the TSB (e.g., ITB17-042b) instructed technicians to replace only the O-ring (P/N 16618-JF00A), the latest revision (ITB17-042D, from March 2021) states the O-ring is no longer available as a separate service part and the entire vent control valve assembly must be replaced.
• A G35Driver forum member 'hoch323' with a P0456 code that appeared only below a half tank of fuel traced the issue to a broken plastic nipple on the EVAP canister where a hose attaches. Replacing the $2.00 dealer part resolved the issue.

Mechanic-Grade Diagnostic Values

• EVAP Canister Vent Control Valve Solenoid Resistance — expected: Approximately 15-16 Ω at 77°F (25°C). Failure: A reading of infinite resistance (open circuit) or zero resistance (short circuit) indicates a failed solenoid coil.
• EVAP Canister Purge Volume Control Solenoid Valve Resistance — expected: Approximately 14.4 - 21.3 Ω at 68°F (20°C). Failure: A reading significantly outside this range indicates a faulty solenoid coil.
• Fuel Tank Pressure (FTP) Sensor Voltage — expected: Approximately 1.3V - 1.7V with the gas cap off (at atmospheric pressure). The sensor operates on a 5V reference.. Failure: A voltage reading that is stuck high (near 5V) or low (near 0V) regardless of system pressure changes points to a faulty sensor or wiring issue.
• EVAP Canister Vent Control Valve Power Supply — expected: 12V+ (battery voltage) on the power wire (often Blue) with ignition ON.. Failure: No voltage indicates a wiring or fuse issue upstream of the valve.

Hidden / Shadow Codes Worth Checking

• Mode $06, Test ID $3C: This is not a DTC, but a monitor within the OBD-II system that specifically tracks the EVAP system's ability to hold pressure for the small leak test. Technicians can view the raw data from this test with an advanced scan tool to see the pressure decay value, even before it's bad enough to trigger the P0456 code. (see via Advanced OBD-II scan tool with Mode $06 data display capabilities.)

Scan Tool Commands That Help

• Infiniti CONSULT-II / CONSULT-III plus: EVAP System Leak Test (in Active Test menu) — This is the dealer-level function used to verify a repair. It allows the technician to command the vent control valve closed, command the purge valve open to draw a vacuum, and then seal the system to monitor the fuel tank pressure sensor reading over time to confirm the system is sealed.
• Professional Bidirectional Scan Tool: Vent Valve ON/OFF Command — Used during diagnosis, especially with a smoke machine. A technician can command the vent valve closed to seal the system. If smoke still escapes from the vent valve area, it confirms the valve itself is leaking and needs replacement.

Wiring & Ground Locations

• EVAP Canister Vent Control Valve Connector — At the rear of the vehicle, on the charcoal canister.. This 2-wire connector provides power and a ground signal from the ECM to the valve. It is exposed to road salt and moisture, and corrosion here can cause intermittent valve operation or a complete failure to close, leading to a P0456 code.
• Main Body Grounds (Fender/Chassis) — The main battery ground connects to the chassis near the battery. Additional braided ground straps connect the engine block to the chassis, often under the air intake tube area.. The ECM and various sensors rely on a clean ground path. While less common, a corroded or loose main ground can cause floating voltages and incorrect readings from sensors like the Fuel Tank Pressure sensor, potentially triggering a false P0456 code.
• EVAP Canister Purge Valve Connector — In the engine bay, on or near the intake manifold.. Provides power and the control signal to the purge valve. A bad connection here can prevent the valve from operating correctly during the EVAP self-test, contributing to a failed test, although it's more likely to cause a purge flow code.

Real Owner Repair Stories

• G35Driver Forum User (Infiniti G35 (saddle-style gas tank)) — Persistent P0456 code.
  ❌ Tried (didn't work) Visual inspection of EVAP hoses
  ✅ What actually fixed it A smoke test revealed a cracked plastic nipple on one of the in-tank fuel pickup assemblies. The hose connecting the two sides of the saddle tank was stressed, causing the nipple to crack over time. The owner performed a DIY repair on the nipple instead of replacing the entire expensive fuel pump assembly.
• G35Driver Forum User 'hoch323' (2006 Infiniti G35 Sedan) — P0456 code would appear only when the fuel tank was at half a tank or less. It would clear after filling up.
  ❌ Tried (didn't work) Replacing gas cap, Replacing solenoids
  ✅ What actually fixed it The user discovered a broken white plastic nipple on the EVAP canister where a hose attaches. The previous owner had attempted a repair with a tar-like substance that eventually failed. Replacing the nipple, a $2.00 part from the dealer, resolved the issue.
• MyG37.com / G35Driver Forum Users (Infiniti G35/G37) — Persistent P0456 code, especially in salt-belt regions.
  ❌ Tried (didn't work) Gas cap replacement, Vent valve replacement
  ✅ What actually fixed it A pinhole leak caused by rust on the fuel filler neck or an adjacent fuel vent return line. The corrosion creates a surface that the gas cap cannot seal against perfectly, or the line itself leaks. Cleaning the filler neck sealing surface with a Scotch-Brite pad or replacing the rusted component was the final fix.

"I Checked Everything" — The Actual Cause

• A cracked nipple on the in-tank fuel pump assembly. A standard smoke test may not reveal this leak if the pressure isn't high enough or if the crack only opens under specific conditions. It required dropping the fuel tank to find and repair.
• A faulty Fuel Tank Pressure (FTP) sensor. If the sensor itself provides an incorrect reading (e.g., it's stuck or slow to respond), the system can pass a smoke test (as there is no physical leak), but the ECM will interpret the sensor's incorrect data as a leak and set the P0456 code.

OEM Part Supersession History

• 14935-AM60A / 14935-AM60B → 14935-JF00A, then 14935-JF00B, 14935-JF00C, and finally 14935-JF00E — Revisions to improve sealing, material durability, and solenoid reliability.
  Heads up: All parts in this chain are generally interchangeable for this application. Using the latest revision (14935-JF00E) is recommended.

Model Year Variations Within This Range

• 2007: The 2007 G35 was sold as both a V35 platform Coupe and a V36 platform Sedan. The EVAP systems are very similar, but component locations and mounting can vary. For example, the vent control valve on the V35 Coupe is typically on a bracket near the canister, while on the V36 Sedan, it is mounted directly onto the canister itself.