What is an EVAP Leak: Big Problem or Nothing to Worry About?

A check engine light can indicate many different problems with your vehicle, ranging from severe failures to minor fixes. And like other engine problems, an EVAP leak can set off your check engine light and send you into a frenzy trying to diagnose the problem. But even if you have the diagnostic trouble code in hand, you might wonder, what is an EVAP leak and how much will it cost to fix?

What is an EVAP Leak?

So, what is an EVAP leak? In short, and EVAP leak code signifies a problem somewhere in the evaporative emission control system (EVAP). The EVAP aims to contain any fumes from gasoline, avoiding spillage into the environment.

But while pollution control is a crucial feature, the EVAP also keeps potentially dangerous fumes from entering the interior of your vehicle. It can also prevent the combustible fuel from causing a more serious problem in your vehicle’s systems.

Potential EVAP Leak Causes

When you see the check engine light pop up on your dash, it’s understandable that you might ignore it. Plenty of small problems set the light off, and most drivers don’t have time to rush off to the shop or order diagnostic tools for home use.

The problem is, a check engine light could be nothing, but it could also be a vital warning sign.

You can find out for sure by running diagnostics on your vehicle. By either stopping in at your local mechanic or auto parts store or hooking up your personal diagnostic device, you can find out what code is causing the check engine light to come on.

Symptoms of an EVAP Leak

Even before you run diagnostics, a few signs can indicate that your check engine light is the result of an EVAP leak rather than some other issue. A symptom such as the smell of gasoline is obvious, but these others can also crop up:

●  Trouble starting the engine

●  Bad fuel economy

●  Rough idling

●  Overall drop in engine performance

In other vehicles, you may not notice any symptoms—and some vehicle systems don’t flip the check engine light on, either.

Common EVAP Leak Codes

For vehicles which show symptoms of an EVAP leak, namely the check engine light, you can use diagnostic tools to find out what error code is causing the light to come on. Depending on the vehicle’s OBD II system, which varies based on the manufacturer and even the make of the car, different codes may crop up.

Common EVAP leak codes include:

●  P0442 Evaporative Emission (EVAP) System Small Leak Detected

●  P0455 Evaporative Emission (EVAP) System Leak Detected (large)

●  P0440 Evaporative Emission (EVAP) System

●  P0446 EVAP Vent Solenoid Valve Control System

●  P0411 EVAP System Control Incorrect Purge Flow

EVAP codes span 0440 to 0457, so there are many other codes to reference depending on your vehicle and its specific problem.

Still, if your vehicle turns back one (or more) of these codes, it may not prove an easy fix. More insight is necessary to determine whether there’s a serious problem or just a minor one.

What Causes EVAP Leak Codes?

Good news for consumers with vehicles not showing any signs of a fuel leak: even if your check engine light is on and you find an EVAP code via the OBD II reading, it might be a simple fix. In other cases, however, it might not be.

Easy Fix: Loose Gas Cap

The most common reason a vehicle shows an EVAP code is because the gas cap is not secure. Especially in modern cars, a gas gap which is even slightly loose can allow fumes to enter the system. While it’s good news for emissions policing and pollution control, it’s frustrating for drivers to find it’s only a loose gas cap which caused them so much stress and financial trouble.

If you’ve recently filled your gas tank, check to make sure the cap is fitted properly and is completely locked. Keep an eye on your fuel efficiency, too, as this can help track whether there’s fuel escaping.

Tightening your gas cap (and clearing the OBD II codes) can solve the problem for many drivers. However, when the check engine light does not go off—AKA the code clears and comes back—that might indicate a more severe problem in the evaporative emission system.

Not So Easy Fixes: Other Fuel System Issues

While a loose gas cap is an easy enough fix, every other issue which spurs an EVAP code isn’t so simple. You might have a leak in the fuel system of your vehicle, which will require further diagnostics and cash flow.

Other issues can involve:

●  Faulty O-ring seals

●  Defective leak detection pumps

●  An inoperative purge valve

●  A leaking vacuum hose or vent

●  Leaks in the EVAP canister

●  Breakage or leakage somewhere else in the system

Is it Safe to Drive with an EVAP Leak?

Most drivers tend to ignore a check engine light, at least until their next service visit. But because an EVAP leak can potentially be a severe and environmentally damaging problem, it’s not a good idea to keep driving with the check engine light on.

Whatever condition your vehicle is in—whether it’s showing symptoms of a fuel leak or not—aim to have the codes pulled as soon as possible. Driving with a fuel leak not only puts you in violation of governmental regulations on pollution and emissions but also leaves you at risk for a vehicle fire or other serious accident.

In the meantime, make sure your fuel cap is tight and check for any visible leaks under the hood. If you have a P0440, P0455, or P0457 code, odds are the gas cap is the issue. For any other code, schedule a mechanic visit as soon as possible to address other potential causes. 

Costs of Repairing an EVAP Leak

Depending on the type of code your vehicle indicates, as well as what parts are faulty or damaged, the cost to repair your car or pickup truck can range from a few dollars to well over four hundred. For example, replacing a gas cap can cost $20 or less, but purchasing a new EVAP canister costs much more.

For example, Ram trucks fuel canister replacements run about two to three hundred dollars. Professional installation and service costs vary widely, too, which can mean a big difference in the bottom line for this type of repair.

Of course, repair costs should top your list of car-buying considerations if you’re in the market for a vehicle. Even when looking at used car values when sticker price is a priority, investigating each brand—or make and model’s—repair costs is a worthwhile endeavor.

Some vehicles, Ford, in particular, have fuel pump shutoff switches which can impact fuel system performance and diagnostics. And it’s not Ford that has quirks which affect diagnosis and repair of EVAP systems. In some cases, it’s easier to do a complete engine rebuild rather than hunt down every leak or vulnerability.

If you must bring your vehicle to a shop for diagnostics, you’ll also be paying the shop rate for the diagnosis time and any physical inspection of the car. Fortunately, handheld OBD II scanners are an easy enough purchase that can help you feel confident about your mechanic’s diagnosis (and the repair bill).

Whatever reason your vehicle is showing EVAP system codes, tracking down and resolving the issue is essential. Whether it’s your safety (and that of your passengers) or the overall level of pollution your vehicle is putting out, there are many good reasons to take heed when your check engine light comes on.