P0455 EVAP system large leak detected

EVAP large leak (gross leak)

Monitor

EVAP faults let fuel vapour escape but rarely change how the car drives, and the main risk is a failed emissions test, so it is safe to drive while you arrange a fix.

It gets more serious if:

  • Inspect soon: You keep smelling raw fuel around the car, not just right after filling up
  • Stop: You see liquid fuel dripping or pooling under the car, or near the filler, tank or canister

Source: how we rate severity

P0455 in short

P0455 means the computer found a large leak in the fuel vapour (EVAP) system. A loose, missing or wrong fuel cap is the most common cause, followed by a split or disconnected EVAP hose. It is usually safe to drive, but stop driving if you see fuel dripping.

Your car stores fuel vapour from the tank in a charcoal canister and later burns it in the engine. To check that this sealed system is not leaking, the computer closes it off and watches whether it holds a vacuum or pressure. If it cannot hold at all, it records a large (gross) leak.

Because the leak is large, the cause is often obvious: a cap left loose or off after refuelling, or a hose that has split or come off. P0456 and P0442 are the same test catching smaller leaks.

The code usually needs the fault to show on two drives in a row before the light comes on. Once fixed, the light goes out by itself after several trips that pass the test.

Most likely causes

These are general causes for this code across vehicles. None is specific to one make or model.

  1. Loose, damaged or non-factory fuel cap

    Common general cause
    Why it ranks here
    A cap left loose or off is the classic large leak, and both EPA and makers name it first.
    What would change this
    Moves down if the cap is factory, clicks and the seal is intact. Moves up if the code started right after refuelling.
    How to test the fuel (gas) cap

  2. Split, cracked or disconnected EVAP hose

    Common general cause
    Why it ranks here
    A hose that is off its fitting or split open makes a leak big enough for the gross-leak test, and FCA has a bulletin for exactly this.
    What would change this
    Rises if you can see a split or loose hose. Falls if a smoke test shows the hoses are tight.
    How to test the vacuum hoses and intake leaks

  3. Filler neck or cap seat not sealing

    Possible — needs testing
    Why it ranks here
    A filler neck or cap seat that does not seal acts like a missing cap. A GM bulletin covers a rolled filler insulator.
    What would change this
    Rises if the rubber around the neck is rolled or the neck is damaged.
    How to test the fuel (gas) cap

  4. Canister vent valve that does not seal, or is fouled by dust

    Possible — needs testing
    Why it ranks here
    GM has linked P0455 to dust fouling the vent solenoid on trucks used in very dusty conditions.
    What would change this
    Rises if P0446 or P0449 is also stored or the truck sees dusty use.
    How to test the evap canister vent valve

  5. Purge valve leaking or not opening when commanded

    Possible — needs testing
    Why it ranks here
    A purge valve that never opens can stop the system building vacuum during the test, which looks like a gross leak. VW lists P0455 among purge-valve codes.
    What would change this
    Rises if P0441 is also stored or the valve fails a commanded vacuum check.
    How to test the evap canister purge valve

  6. Leaking or contaminated charcoal canister

    Possible — needs testing
    Why it ranks here
    A cracked canister can leak, but this is less common than cap or hose faults.
    What would change this
    Only confirmed by smoke escaping at the canister body.
    How to test the evap charcoal canister

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Remove and refit the fuel cap. Check it is a factory or OEM-equivalent cap, that it clicks when tightened, and that its seal is not cut, cracked or rolled.

    Low risk

    • IfThe cap was loose, missing, non-factory or has a damaged seal

      It meansThe cap is the most likely leak. Tighten or replace it and let the system re-check over the next few days.

      Points to: Loose, damaged or non-factory fuel cap

    • IfThe cap is factory, clicks and the seal looks good

      It meansLook further along the system.

      Go to step 2

  2. Read all stored and pending codes with a scan tool and note which other EVAP codes are present.

    Low riskTool: OBD-II scan tool

  3. With the engine off and cool, look over the EVAP hoses and connectors you can reach at the purge valve, the canister and the filler neck.

    Use cautionTool: flashlight

    Warning:Fuel vapour is flammable. Work outdoors with the engine off and cool, and keep sparks, cigarettes and open flames away.

  4. Have a shop smoke test the EVAP system with the vent side sealed and look for smoke escaping.

    Best left to a shopTool: EVAP smoke machine

    Warning:Shop test. The setup has to match how the system is tested (pressure or vacuum), and fuel vapour is flammable.

  5. Have the shop command the vent and purge valves with a scan tool and check each one holds vacuum with a hand vacuum pump.

    Best left to a shopTool: scan tool with output controls, hand vacuum pump

    Warning:Shop test on the fuel vapour system.

Symptoms

  • Check engine light on, usually with no change in how the car drives
  • "Check fuel cap" message on cars that have one
  • Fails an emissions or smog test because of the light or an incomplete EVAP monitor
  • Persistent raw fuel smell around the car Gets more serious: stop and have it checked.
  • Liquid fuel dripping under the car Gets more serious: stop and have it checked.

Compare with: Check engine light came on after getting gas

How to fix

  1. Check the fuel cap is a factory or OEM-equivalent part, then tighten it until it clicks.

    Warning:Engine off, no smoking or flames near the filler.

  2. Look at the cap seal for cuts, cracks or a rolled o-ring and replace the cap if it is damaged.

  3. Stop filling once the pump clicks off the first time. Topping off can flood the canister.

  4. After a repair, drive normally for several days so the monitor can re-run. Clearing codes or disconnecting the battery resets readiness, so do it shortly before an inspection only if you then complete a drive cycle.

Parts and cost context

  • Fuel (gas) cap:A factory or OEM-equivalent cap is the cheapest first step. Toyota, for example, says to use only a genuine cap.
  • EVAP charcoal canister:Replace the canister only after a smoke test confirms it is leaking. Labour varies, so get a quote.
  • EVAP canister vent valve:Often mounted near the canister or tank. Labour varies, so get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Chevrolet

  • 2019–2025 · Silverado 1500

    Supported by vehicle data

    GM bulletin 23-NA-073 links P0455, P0442, P0446 and P0449 on these trucks to dust plugging the canister and vent solenoid in very dusty use. Silverado 2500 HD and 3500 HD (2020–2025) are also covered. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

  • 23-NA-073Status unverified

    P0442, P0446, P0455 or P0449 from dust plugging the EVAP canister and vent solenoid

    2019–2025silverado-1500, silverado-2500-hd, silverado-3500-hd · issued · NHTSA MC-11016945

    In very dusty use, dust can get into the canister and vent solenoid and set leak or vent codes. GM prescribes adding an inline filter between the canister and its fresh-air inlet, paid by the customer, and treats the filter as a maintenance item. The same bulletin covers GMC Sierra 1500 (2019–2025) and Sierra 2500 HD/3500 HD (2020–2025); cab-and-chassis (ZW9) trucks are excluded.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

GMC

  • 2019–2025 · Sierra 1500

    Supported by vehicle data

    The same GM bulletin (23-NA-073) covers the Sierra 1500 and the 2020–2025 Sierra 2500 HD/3500 HD for P0455, P0442, P0446 and P0449 caused by dust in the canister and vent solenoid. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

  • 23-NA-073Status unverified

    P0442, P0446, P0455 or P0449 from dust plugging the EVAP canister and vent solenoid

    2019–2025silverado-1500, silverado-2500-hd, silverado-3500-hd · issued · NHTSA MC-11016945

    In very dusty use, dust can get into the canister and vent solenoid and set leak or vent codes. GM prescribes adding an inline filter between the canister and its fresh-air inlet, paid by the customer, and treats the filter as a maintenance item. The same bulletin covers GMC Sierra 1500 (2019–2025) and Sierra 2500 HD/3500 HD (2020–2025); cab-and-chassis (ZW9) trucks are excluded.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Jeep

  • 2015 · Grand Cherokee

    Supported by vehicle data

    FCA bulletin 25-002-15 REV. A links P0455 and P0456 on vehicles built 16 Nov 2014 to 17 Jan 2015 to a split hose at the purge valve. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:Hose at the purge valve

  • 25-002-15Status unverified

    P0455 and/or P0456 from a split purge valve hose

    2015grand-cherokee · issued · rev. REV. A · NHTSA MC-10151727

    On vehicles built 16 November 2014 to 17 January 2015, the hose at the purge valve can split and set large or small leak codes. Replace the hose. The bulletin also covers the 2015 Dodge Durango built in the same window.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Dodge

  • 2015 · Durango

    Supported by vehicle data

    The same FCA bulletin (25-002-15 REV. A) covers Durangos built in the same window for P0455 and P0456 caused by a split purge valve hose. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:Hose at the purge valve

  • 25-002-15Status unverified

    P0455 and/or P0456 from a split purge valve hose

    2015grand-cherokee · issued · rev. REV. A · NHTSA MC-10151727

    On vehicles built 16 November 2014 to 17 January 2015, the hose at the purge valve can split and set large or small leak codes. Replace the hose. The bulletin also covers the 2015 Dodge Durango built in the same window.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0456EVAP system very small leak detected

    Same system Common general cause

    Same leak test, different leak size. P0455 is the large leak, P0456 the very small one, so the hunt for P0456 takes much finer testing.

  • P0442EVAP system small leak detected

    Same system Common general cause

    Same leak test at a smaller size. A cap that is loose enough sets P0455; a seal that is only slightly worn tends to set P0442.

  • P0446EVAP vent control performance problem

    Shares causes Supported by vehicle data

    GM links P0455 and the vent code P0446 to the same dust-fouled vent solenoid on some trucks.

  • P0449EVAP vent valve circuit fault

    Shares causes Supported by vehicle data

    GM links P0455 and the vent circuit code P0449 to the same dust-fouled vent solenoid on some trucks.

  • P0457EVAP leak detected from the fuel cap being loose or off

    Shares causes Supported by vehicle data

    Ford's SSM 51719 covers P0457 and/or P0455 from a fuel cap not installed properly or debris on its seal, so check the cap first.

All EVAP (evaporative emissions) codes

P0455 questions

Can a loose gas cap really cause this code?

Yes. OBD systems can detect the vapour leak from a cap that is not tightened. After you tighten or replace it, the light should go out by itself once the system re-checks and passes on later drives, which can take several trips.

What is the difference between P0455, P0456 and P0442?

They come from the same leak test. P0455 means the system could not hold vacuum or pressure at all, a large leak. P0442 is a small leak and P0456 a very small one, so the smaller the leak, the harder it is to find without a smoke test.

Is it safe to keep driving?

Usually yes, as long as there is no strong fuel smell and no fuel dripping. Most makers advise getting it fixed when it is convenient. A strong fuel smell means get it checked soon, and dripping fuel means stop and do not drive.

Will this code fail an emissions inspection?

In states that test OBD-II, a check engine light that stays on with the engine running fails the test. Clearing the code does not help straight away, because the EVAP monitor then reads not ready until the car completes a drive cycle.

Sources and review

  1. Frequently Asked Questions on On-Board Diagnostics (EPA 420-F-97-003) — US EPA ,
  2. On-Board Diagnostic II (OBD II) Systems Fact Sheet — California Air Resources Board ,
  3. EVAP: The Phantom Emissions Menace (Nissan TechNews, May 2018) — Nissan North America (hosted by AutomotiveTechInfo) ,
  4. OBD Test Reference (rev 8.6) — California Bureau of Automotive Repair ,
  5. What do you mean my car is not ready? — New York State DMV
  6. Recall acknowledgement 17V-088: BMW i3 REx fuel tank vent line may chafe — BMW of North America / NHTSA
  7. Part 573 Safety Recall Report 15V-621 (Mazda 8615J): liquid fuel can enter the EVAP canister — Mazda North American Operations / NHTSA
  8. What To Do With the Check Engine Light (EPA420-F-00-041) — US EPA ,
  9. Toyota Camry Owner's Manual (OM06291U, 2.5L A25A-FKS / 3.5L 2GR-FKS) — Toyota
  10. FCA 25-002-15 REV. A: P0455 and/or P0456 from a split purge valve hose — FCA US / NHTSA ,
  11. GM PIC6030: P0442 from fuel filler pocket insulator rolled over the filler neck — General Motors / NHTSA ,
  12. GM PI0979: P0442 from a vent solenoid that leaks under vacuum — General Motors / NHTSA ,
  13. GM 23-NA-073: P0442, P0446, P0455 or P0449 from dust intrusion into the canister and vent solenoid — General Motors / NHTSA ,
  14. VW 20 17 02: EVAP purge valve (N80) diagnosis — Volkswagen of America / NHTSA ,
  15. GM 22-NA-217: P0442 from a purge canister weld leak — General Motors / NHTSA ,
  16. Driveability Corner, August 2014 (Mark Warren) — MOTOR Magazine ,
  17. Cal. Code Regs. Tit. 13, § 1968.2 — Malfunction and Diagnostic System Requirements (OBD II) — California Air Resources Board (via Cornell LII)
  18. Ford SSM 51719: P0457 and/or P0455 from fuel cap installation or debris on the cap seal — Ford Motor Company / NHTSA ,
Last reviewed
Written by
Saurabh K.
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