P0442 Code: Small EVAP Leak, Causes and How to Fix It

A P0442 code, which many owners type as PO442, is the "small leak" code of the evaporative emission (EVAP) system. That's the sealed set of hoses, valves and a charcoal canister that keeps fuel vapor out of the air.

The first advice you'll get is to check the gas cap, and it's the right place to start because it's free. The code stored beside it can narrow the search for free, and a smoke test then usually finds the hole itself.

What does a P0442 code mean?

P0442 means the sealed fuel vapor system is leaking, and the leak is at least as big as a 0.040-inch hole, about a millimeter across, or several small leaks adding up to one. The car tests the whole system as one piece, from the gas cap to the charcoal canister that stores the vapor.

California's OBD-II rule, the on-board diagnostics standard carmakers build to across the US, sets that size. A smaller 0.020-inch leak sets P0456 instead, and a large one P0455.

You may also see it written P0442-00 or P0442:00, which is the same code. The P0440 page maps the whole EVAP family.

Can you drive with a P0442 code?

Yes, unless one of the signs below shows up, because a vapor leak this small doesn't feed or stop the engine. You may fail an emissions test, but P0442 alone isn't an emergency. On a 2012–2018 Focus 2.0L, run the VIN first, since a purge valve recall there covers a stall while driving.

The exceptions are signs of liquid fuel or a fault that reaches the engine. A gas smell, fuel on the ground or a stall means more than a pinhole, and leaking fuel is a fire risk.

We'd stop driving and get it checked if:

• You smell gasoline. Inside the car, or outside it in a way that doesn't fade.
• Fuel drips or pools under the car. One owner's filler tube leaked gas onto the ground while filling.
• Another warning comes on. A flashing check engine light or any other engine or temperature warning means more than this code.
• It stalls, while driving or after a fill-up, or won't restart. Some owners who reported it also had a purge code, so have the purge valve tested.

What are the symptoms of a P0442 code?

You may notice only the check engine light, because a pin-sized vapor leak doesn't touch the fuel the engine runs on. When there's more, owners describe it around filling up, because that's when the system is under the most vapor.

Owners in the federal complaints describe hard starting, stalling or rough running after a fill-up, a fuel smell that can reach the cabin, and a failed inspection where the stored code kept the car from passing. A tank that's hard to fill is the symptom GM names in the title of its vent valve bulletin for its pickups.

What causes a P0442 code?

Any part of the sealed system that lets vapor out: the cap, the canister and its vent valve, the purge valve and its lines, the filler neck and tank, or a leak detection pump on cars that have one. The list below runs from the cap you touch to the tank you can't see.

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P0442 alone confirms none of them, because the code names the size of the leak, not the part. Each cause comes with its clue and the test that names it.

1. The gas cap and its seal

On a car with a cap, it seals the filler with a rubber ring, and a cap that's loose, cracked or has a twisted or dirty seal leaks while it still clicks. Audi's fix is to refit a twisted seal and replace the cap only if the leak comes back.

Other carmakers replace the cap or free a binding tether. Check it once, and properly, because a cap isn't a cure-all: owners in the complaints replaced one and the light came back.

Some Fords have no cap at all, a capless fuel system, so on those cars skip to the VIN and the smoke test. Don't prop the filler flap open to look.

2. The canister and its vent valve

The canister is the box of charcoal that holds the vapor, and the vent valve on its fresh-air side closes so the system can be tested. A cracked canister, a leaking O-ring between the two, or dust and water in the vent valve all let the test fail.

GM has the most fixes here, and on its trucks and SUVs the fix in two bulletins is a sealed vent valve or a filter rather than a canister. GM also tells technicians not to replace the canister unless it fails the leak test or has taken in too much dirt, dust or water.

3. The purge valve and its lines

The purge valve, also called the purge solenoid, lets stored vapor into the engine, and the lines to it run along the body where they can chafe or come loose. A valve that leaks when shut, or a pipe rubbed through or not pushed home, lets vapor escape before the boundary of the test.

GM recalled the 2016–2019 Chevrolet Volt for a pipe at the purge valve that chafes on an A/C hose, and Ford found a line chafing on another hose in the 2022–2024 Maverick. Owners' complaints name the valve too, including one dealer that replaced the same purge solenoid twice in three months.

4. The filler neck and the tank

The filler neck runs from the cap down to the tank, and the tank carries a pump module with a seal on top. Rust on the neck, a cracked module flange or a damaged seal can all leak vapor, and sometimes liquid fuel.

A shop may need to lower the tank to reach these parts. Kia's bulletin tells technicians to check the lines and cap first and then look for a damaged fuel pump seal, and Toyota's bulletin on an older Camry names a fuel filler tube improvement.

Smoke finds the hole

How do you fix a P0442 code?

Start with the cap seal, then let a smoke test find the leak rather than buying parts in turn. Go in this order, and the first three steps cost little or nothing:

1. Read and save every code. Write down P0442 and anything beside it, because P0456, P0455, P0446, P0441 or P0496 each narrows where to look.
2. Check the cap seal, once, if your car has a cap. Take the cap off, look at the rubber ring for a twist, crack, flat spot or grit, refit it until it clicks.
3. Run the VIN. A dealer checks bulletins and recalls by VIN, the 17-character vehicle identification number, and our free VIN checker lists the recall campaigns for your car's model year. Some Focus purge valves are under a recall for a fault that can stall the engine while driving.
4. Ask for a smoke test. The shop's smoke machine pushes harmless visible vapor into the sealed system and watches where it escapes. Ask what it costs before agreeing, as its own line on the estimate.
5. Replace only what the test found. Clear the code after the repair and drive normally until the monitor reads ready again.

If the VIN check finds no bulletin, the smoke test still decides, because step 2 can't find a leak past the cap. If the light comes back after a new part, ask for the test again before buying the next one, and if the smoke test finds nothing, ask whether the leak shows up only with a full tank, as one owner's smell did.

How much does it cost to fix a P0442 code?

A revised vent valve on a 2015 Silverado 1500 runs $185–$342 at an independent shop, parts and labor, on GM's 1.1 hours. A vapor canister with its purge valve on a 2014 Focus 5-door runs $261–$545, parts and labor, on Ford's 1.1 hours.

Check what's free first: refitting the gas cap costs nothing, and Ford replaces some Focus purge valves free under a program, so run the VIN before you pay. Past the cap, a smoke test runs $100–$200 at a shop, and the leak test decides which part you pay for.

Where the tank has to come down, labor is most of the bill, so ask for the test result, hours and rate on the written quote, and whether the diagnosis fee comes off if you approve the repair. The rates behind these figures are on how we price repairs.

Will a P0442 code fail an emissions test?

It can, in states that read the car's computer, and clearing it first doesn't help. A code that has the light on fails there, and erasing it leaves the evaporative monitor reading "not ready", which may also be rejected depending on the state and the car's model year.

Only driving sets the monitor back to ready, because the check runs by itself when its conditions are met. Ask the shop how much driving your car needs after the repair before you go back for the test.

Which codes come with P0442?

Carmakers' bulletins list P0442 with other EVAP codes, and a second code stored on your car is a free clue to where the leak is. Four leak and flow codes are listed with it, and each one changes where to look.

In the complaints, only 5 of the 22 owners named a second code, and P0496, a purge flow code, was the one named most, by three owners who all described trouble after filling up. Toyota's bulletins on Toyota and Lexus models treat P0441, P0442 and P0446 as a set.

Is P0442 common on a Chevy?

Yes, Chevy leads the owner complaints that name this code. GM brands hold 14 of the 22, and 11 of those are Chevrolets.

GM's own documents explain why: dust and water reaching the canister and its vent valve on several trucks and SUVs. So on a GM truck or SUV, the vent valve is the first part to test.

The count shows where owners wrote in, not how often a part fails. Ford owners report the smaller leak code, P0456, far more often than this one.

Common questions

Asked most often

What is the most common cause of a P0442 code?

The cap is the cheapest to check, but no document counts how often each part causes it, and all four complaint owners who replaced a cap saw the light come back. Carmakers' bulletins name the cap seal, the canister and its vent valve, the purge valve and its lines, and the filler neck.

How do you fix P0442 without replacing the EVAP canister?

Check the cap seal, then ask for a smoke test. GM tells its technicians not to replace the canister unless it fails the leak test or has taken in too much dirt, dust or water, and its pickup fix is a sealed vent valve.

Will a P0442 code clear itself?

The light can go out on its own once the leak test runs and passes on later drives. If it was a cap left loose once, that's the fix, and if the light returns, the leak is still there.

What does P0442 mean on a Ford?

In the federal complaints, 78 Ford owners name P0456 and 2 name P0442, so check which code you have. Both of those were Focus cars with a deformed fuel tank, which Ford recall 18V-735 traces to a purge valve stuck open, a fault that can also stall the engine.

Prices are ranges compiled in November 2026 for the US market and vary by region, engine and shop rate. Prices from $10 up are rounded to the nearest dollar. Below $10 they're exact. This article is general information, not advice about your specific vehicle. See the disclaimer.