P0456 Code: Will It Clear Itself, and What It Costs

OilAndMiles.com - Every result for a P0456 code tells you to check the gas cap. That advice is right, and it isn't what brought you this far down the page.

What brings people here is the version where the cap was tightened, or a vent valve was replaced, or a thousand dollars was spent, and the light came back a week later. That has an explanation, it's written into the regulation, and almost nobody publishes it.

The second thing almost nobody publishes is that the answer changes with the badge on the hood. We read the makers' own service bulletins for the five names people ask about most, and on one of those cars the repair you're about to pay for may already be covered.

The filler, where most P0456 codes start

What does a P0456 code mean?

Your car tests its own fuel vapor system for leaks, and P0456 is what it stores when it finds the smallest leak it is required to find: about 0.020 inches, the width of a pencil lead.

That system has one job, and it isn't making the engine run. It catches gasoline fumes rising off the tank, holds them in a charcoal canister, and feeds them to the engine to be burned instead of letting them reach the air. A hole in it changes nothing you can feel, hear or smell.

So the code isn't a warning that something is about to break. It is a failed emissions test stored in advance, and it will fail a real one in any state that runs them. That's the whole practical consequence.

You'll also see it written PO456, with a letter O. There's no such code. The second character is a zero, and that is how every scanner and every repair order prints it.

Why does a P0456 code only show up on cold mornings?

Because the test itself hardly ever runs. The car only attempts it after a cold start, inside a narrow temperature window, with the tank neither full nor nearly empty, and most weeks those never line up.

The leak test isn't running while you drive. The regulation only lets the car attempt it under a narrow set of conditions.

Those conditions come from the California OBD II regulation, 13 CCR 1968.2, which the EPA accepts in place of its own. This is why a car can drive for a week after a repair and look fixed.

So a car in a cold snap, or a heatwave, or one that gets short trips on a full tank, can go a week or more without attempting the check at all. The code isn't intermittent. The testing is.

Will a P0456 code clear itself?

The lamp will. The code mostly won't. And neither of those means the leak has gone.

For most faults the car turns the lamp off by itself after three sequential driving cycles in which the monitor ran and found nothing. That sounds like proof and it's the trap: if the conditions were never met, the monitor never ran, nothing was tested, and the lamp went out anyway.

The stored code stays in memory for around forty warm-up cycles regardless, which is why it's worth having the codes read even after the light has gone. A dark dash is the weakest evidence on the car.

That's why the advice you find on this question contradicts itself. Three drive cycles and forty warm-up cycles are both real numbers, and they describe different things: one is when the lamp goes out, the other is when the memory lets go.

Why did the repair look like it worked?

Because clearing the codes turns the lamp off that minute, while the car needs days of the right conditions before it tests the repair at all. The proof and the repair are separated by a week.

A shop replaces a part, clears the codes and hands the car back with no light on the dash, which feels like proof. Then over the following week the conditions finally line up, the monitor runs for the first time since the repair, and it finds the leak that was always there somewhere else in the system.

The lamp going out at the counter proves the codes were cleared. It proves nothing about the leak. The only evidence that matters is the monitor running again and passing, and neither you nor the shop controls when that happens.

The practical version: before paying for a second part, ask whether the monitor has actually run and passed since the first one. A scan tool reports readiness status, and it's a different question from whether there is a code.

What does P0456 mean on a Ford, Jeep, Dodge, Ram or Chrysler?

More than half of every P0456 complaint in the national record carries one badge. Four of the other five makes share a part no other manufacturer uses. So the answer really does change with the car.

From the national complaint record

0.25%

of Ford Focus complaints name P0456. That's three times the next one, so this isn't a leaderboard with a close race at the top. It's one outlier and a pack.

Share of each vehicle's NHTSA complaints that name P0456, model years 2010 to 2025, 645,169 complaints read; the Ford Focus (0.25%) is left out of the bars because at that distance every other bar would be a hairline.

Ford Edge		0.09%	10 of 11,493
Ford Escape		0.07%	12 of 18,302
Ford Fusion		0.06%	11 of 18,153

We should say plainly how small that base is: 145 mentions divided across 19 makes is thin, and these count owners who filed a complaint rather than cars that failed. Take it as a pattern in how the codes are reported, not as a reliability ranking.

P0456 on a Ford

Ford accounts for 78 of the 145 P0456 mentions, more than half of them, with the Focus alone at 32, the Escape at 12, the Fusion at 11 and the Edge at 10. The heaviest single model year is 2018.

The purge valve is named in 31 of those 78, and Ford's own paperwork explains why. In October 2018 it issued recall 18V-735 for 2012 to 2018 Focus cars, because the canister purge valve could stick open and the engine computer's software didn't reliably notice. A purge valve stuck open holds vacuum on the fuel vapor system, and Ford's filing says that can deform the fuel tank until it collapses on itself.

That didn't settle it. A second recall in July 2019, 19V-515, covered cars whose new calibration hadn't been installed properly at the factory. In September 2023 NHTSA reopened the question again, after 98 more complaints of lost power.

The Focus, the car this code is filed against most

P0456 on a Jeep

Jeep is second with 12 of the 145, and 8 of those are the Grand Cherokee. Twelve is a thin base, so read it as where owner attention went rather than as a failure rate.

One Jeep case is documented exactly. In April 2020 FCA issued bulletin 18-035-20 for the 2020 Grand Cherokee and the 2020 Dodge Durango with the 3.6L engine, built between 4 November 2019 and 9 March 2020. Its subject line is Fuel Vapor Hose Not Connected.

A hose in the left rear wheel well was leaving the factory unplugged. The codes the bulletin lists are P0441, P0455 and P0456, along with a fuel smell at that same wheel. The repair is to take the wheel off, pull the liner down and push the connector back together, and the work is covered by warranty.

P0456 on a Dodge

Dodge has 7 of the 145, two for the Charger and one each for the Ram 1500, Journey, Grand Caravan, Challenger and Durango. Seven complaints across six models isn't a pattern, and we're not going to present it as one.

What does carry over is the paperwork either side of it. The Durango shares the disconnected vapor hose above with the Grand Cherokee, and the 2013 Journey appears in the software bulletin under Chrysler below.

P0456 on a Ram

One complaint, a 2019 Ram 1500. That's not a finding, and we won't dress it up as one.

What's true of every Ram is the architecture it shares with the rest of the group. Stellantis runs the leak test through a part called the ESIM, and the ESIM is a mechanical switch rather than a sensor. Inside are two weighted valves and a rubber diaphragm, mounted upright so gravity holds the valves shut, sitting on the charcoal canister under the vehicle.

A Ram 1500 on a winter morning

When the diaphragm splits or the contacts corrode, the switch stops closing. The computer reads that as a leak whether or not one exists, and that's why a smoke test on these can find nothing at all.

P0456 on a Chrysler

Chrysler has 7 of the 145, spread across four models: three Town & Country, two 200, a 300 and a Pacifica. That's too few to call a pattern. The year is the pattern.

Four of those cars are 2013s, and 2013 is a year Chrysler wrote a bulletin about.

FCA bulletin 18-050-16, issued 27 April 2016, covers exactly that year: the 2013 Chrysler 200, Town & Country, Dodge Grand Caravan and Journey. It lists P0456 among the codes owners were seeing, and the remedy isn't a part at all. It's a software reflash of the engine computer.

On those cars the leak was in the logic rather than the hoses.

One instruction runs across all four of those brands. Bulletin 18-048-23 covers every 2012 to 2023 Stellantis vehicle, and it makes a scan tool leak test mandatory before and after any P0456 repair. Its reason is a single line: a road test won't confirm the repair, because P0456 is only set with multiple engine off and drive cycles, which can't be reproduced during a dealer visit.

That's the manufacturer telling its own dealers what the cold-start section told you.

How much does it cost to fix a P0456 code?

Between $3.93 and $225 for the part alone, and the honest answer is that the car decides which end you're at. Six parts can set this code and they're priced below for three of the cars people ask about most, every brand the catalog lists, with the one fitted repair average the country has.

Cheapest first, because the odds genuinely run that way.

Work down this list rather than starting at the bottom of it:

1. The gas cap. Off, inspect the seal, back on until it clicks. There's a code just for this one, P0457, which is the rule conceding how often it's the answer. If the car fills capless, as a Grand Cherokee does, there's no cap to check and the funnel inside the filler seals it instead.
2. The vent valve. Under the car at the charcoal canister, where road spray and salt reach it. P0446 and P0449 point here.
3. The purge valve. Under the hood, and the sixth most common repair in the United States. P0441, P0443 and P0496 point here.
4. Hoses and the canister. The expensive end, and the only row with a three figure part: the canister runs $69 to $225 before anyone fits it. A smoke test is how it gets found rather than a part swap. Still nowhere near the $1,511 a converter costs.

The odds are good news. The valve you're most likely to need is the cheapest thing on a national top ten whose first entry is a catalytic converter at $1,511.

Are P0456, P0442 and P0455 the same test?

No. It's one monitor measuring one thing, the size of the hole, and the three codes are three thresholds on that one measurement.

We took those thresholds from the federal rule rather than from a code lookup, because the lookups give each code its own page, and that's what makes them look like three separate faults.

They aren't three different faults. The car pressurizes the fuel vapor system, watches whether the pressure holds, and reports which threshold it failed. The thresholds come from federal rule 40 CFR 86.1806-17, which requires the system to find a leak of 0.020 inches and even names the test orifice by manufacturer and part type.

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Half a millimeter, in a system of hoses, a plastic canister and two valves running the length of the car. You can't see it, hear it or smell it. That single fact explains most of this page.

Does the threshold depend on who built the car?

Which of the three thresholds your car reports turns out to depend heavily on who built it. In the complaints read for this article, P0456 is named 128 times and P0442 18 times, and the two barely appear on the same badge.

Ford, as the section on badges showed, names P0456 68 times and P0442 exactly once. Chevrolet is the mirror image: 9 P0442 mentions and not a single P0456, spread thinly across the Corvette, Impala and Sonic. Buick and GMC, both General Motors, sit on the P0442 side as well.

That's not two different faults. It's the same leak test with the manufacturer having chosen which threshold to report first, so the code on your scanner tells you as much about the badge on the hood as about the size of the hole. If you own a Ford and you're reading about P0442 because a forum told you it is the same thing, it is, and your car will probably never show it.

What if you get two EVAP codes together?

A common and confusing case, and it isn't two problems. P0455 and P0456 arriving together usually means one leak large enough to fail the gross test, which then also fails the small one. Treat it as a single leak and start at the same place.

What genuinely does point somewhere different is a leak code alongside a flow code, P0441 or P0496. Those describe purge volume rather than a hole, and a third kind again is the circuit test behind P0443, so a valve stuck open can produce both at once, and in that case the valve is the sensible first move rather than the cap.

Can you drive with a P0456 code?

Yes, and this is one of the few codes where that answer needs no caveat about load or distance. The evaporative system exists to stop fuel vapor reaching the atmosphere. It has no role in how the engine runs, so there's nothing to damage by driving and nothing to feel.

Two real consequences. It fails an emissions test in a state that runs one, and so does a car whose codes were cleared too recently for the monitors to have finished. And a leak means fuel vapor escaping, which is a slow loss rather than a hazard on a car that is otherwise sound.

If the light is flashing rather than steady, that's a different code and a different article. An evaporative fault doesn't flash.

How do you fix a P0456 code?

By finding the hole, not by replacing the part that looks likeliest. A shop fills the sealed side of the system with low pressure smoke and watches where it escapes, and that's the only test that finds a 0.020 inch leak reliably. Everything above about caps and valves is the cheap end of the odds, and the smoke test is what settles the rest.

So ask for the smoke test by name, and ask what it costs before the parts conversation starts. A quote that names a part before anyone has smoked the system is a guess with an invoice attached, and this article exists because that guess so often comes back a week later.

Then ask for one thing more: that the leak monitor is run and passed before you collect the car, on a scan tool, not on a road test. Stellantis made that mandatory on every 2012 to 2023 vehicle in bulletin 18-048-23 for exactly the reason this whole page describes. Without it, neither you nor the shop knows whether the repair worked, and you find out on a cold morning.

Common questions

Asked most often

How do you fix a P0456 code?

Start with the gas cap, which costs nothing to check, or the funnel in the filler if the car fills capless. Then the vent valve on a Ford, or the ESIM on a Jeep, Dodge, Ram or Chrysler. Then the purge valve, $172 fitted. The canister is last: dearest on the list, and a smoke test is what finds it.

How much does it cost to fix a P0456 code?

Fitting an EVAP purge valve averaged $172 in the United States in 2025, the cheapest repair on the national top ten. At the counter the parts are nowhere near each other: a capless funnel $3.93, a gas cap $7.24 to $26, a purge valve $19 to $59, a charcoal canister $69 to $225.

Is it okay to drive with a P0456 code?

Yes. An evaporative leak has no effect on how the car runs, drives or stops. It will fail an emissions test in a state that runs one, and that's the whole practical consequence.

Why does my P0456 only come on during cold starts?

Because that is when the car tests. The regulation only lets the leak check run after a cold start, between 40 and 95 °F, with fuel in a set range. The leak is there all day; the test isn't.

Why did the code come back after I replaced the part?

Either the leak was somewhere else, or the test had not run yet when you drove away. A car can go days without the conditions for it, so a lamp that went out isn't proof that anything was repaired.

What is the difference between P0456, P0442 and P0455?

Size, not system. They're one test read at three thresholds: P0456 is the very small leak at around 0.020 inches, P0442 the small one, and P0455 a gross leak such as a cap left off.

Can a loose gas cap cause a P0456?

Yes, and the rule concedes it: there's a code, P0457, that exists specifically for a leak detected with the fuel cap loose or off. Take the cap off, check the seal, and put it back until it clicks.

Prices are US averages compiled in September 2026 and vary by region, engine and shop rate. Prices from $10 up are rounded to the nearest dollar, so $14.13 reads as $14 and $14.52 as $15. Below $10 they're exact. This article is general information, not advice about your specific vehicle, see the disclaimer.