In the days gone by, you would watch as your grandfather would listen, wiggle, and wrench his vehicle back to life. Although this is still a good method to diagnose mechanical issues, in the modern era, we also have the check engine light codes to help us out. An essential component in any diagnostic process, they allow you to narrow down your issue to one system.

The P0442 code, which we’ll cover in this guide,  gives you pin-point accurate data your grandfather could only dream of. Being an EVAP code, trying to diagnose this error without using an OBDII scanner would be borderline impossible. There are simply too many components you’d have to inspect, and some of them are not easy to reach at all. This guide will explain what the code means, the symptoms, and anything else you might need to know.

What is the P0442 Code, and What Does It Mean? 

The P0442 code is a diagnostic trouble code that your PCM logs when there is a fault in the EVAP system. There are a few other EVAP system codes. A P0442 code is a specific indication that there is a small leak. Larger, more severe leaks will trip a different code and require a different approach to troubleshooting.

What Is an EVAP System? 

Gasoline evaporates at low temperatures. If you’ve ever spilled a couple of drops while filling up your car, you know how fast it disappears from the ground. You can even smell the gas vapors while filling up.

These vapors are bad news for the atmosphere, so in 1996, manufacturers were mandated to add the EVAP (Evaporative Emission Control System) to all new vehicles. The idea behind modern EVAP systems is to have them monitor the gas tank, fuel lines and watch for any leaks. Any vapors that do escape are trapped in a charcoal canister. It then releases them into the engine using a canister purge valve when the engine is warm.

EVAP systems rarely impact the performance of the vehicle in any meaningful way. Even when it malfunctions, there are rarely any serious consequences aside from increased fuel consumption. In most cases, you’ll just have that check engine light illuminating your dash, which can be pretty annoying. 

What Are the Common Symptoms of a P0442 Fault Code?

The P0442 code is specific to the EVAP system, so all the symptoms will be relegated to it. However, the immediate symptoms don’t tell you much about the issue, but there are a few that can help in the diagnosis process:

• Check Engine Light
• Gas Smell
• Increased vehicle emissions
• Reduced fuel economy

Check Engine Light

As with any emissions issue, the check engine light will illuminate when there is an issue. In modern vehicles, so much as a pinprick in the EVAP hose can cause the check engine light (CEL). That being said, you can never know what the CEL is about until you plug in that OBD II reader. It can be something as benign as a small EVAP leak, but it can also indicate a much more serious problem with your car. As such, a CEL shouldn’t be ignored for long. 

Gas Smell

Gasoline vapors give off a distinct smell. You may not notice it while driving, but because fuel lines are generally found on the driver’s side, a strong (or mild) smell of gas will be noticeable when entering the vehicle if there’s a vapor leak somewhere along the fuel lines. While this doesn’t have to be a serious thing, you should definitely look into the origin of the gasoline smell for obvious reasons. 

Increased Vehicle Emissions

The EVAP system reduces emissions caused by gas vapors while the vehicle is off. So naturally  it can increase the one symptom of an EVAP system failure — increased emissions. The problem with increased emissions is they rarely cause issues that prevent you from driving your vehicle, but will cause you to fail your annual emissions test.

Reduced Gas Mileage

This problem is specifically related to the canister purge valve. A failing CPV can cause gas vapors that would usually enter the engine to vent out into the environment. In a way, that deprives the engine of fuel that it would otherwise use to run the car. While you won’t notice a massive reduction in gas mileage, the loss of gas vapors can add up over time.

What Are the Common Causes of P0442 Fault Code?

You can either solve this issue in five minutes or five hours, it all depends on the cause. The causes vary drastically in terms of how long the troubleshooting process will take, and how much time the repairs will take. 

They also vary in commonality. A gas cap failure is much more likely than a hose failure. There are some other causes that can lead to a P0442 code. These include:

• Gas cap failure
• Gas tank leaks
• Faulty EVAP canister
• EVAP Solenoid and Hose damage
• PCM flaws

Gas Cap Failure

Your gas cap prevents vapor from escaping the gas tank and any fuel from spilling out while you drive. A loose, damaged, missing, or wrong gas cap can cause a P0442 fault code. That’s why most technicians first check to see if the gas cap is on tight before they pull out the big guns. 

Gas Tank Leaks

Most gas leaks occur at the bottom of the tank, and in that case, you’ll notice them almost immediately. Leaks from the top of the fuel tank can be less common and more difficult to diagnose. They cause the P0442 code as vapor rises from the tank and leaks from the holes. That being said, a faulty gas tank should be among the last things to check. 

Faulty EVAP Canister

As with any part, the EVAP systems carbon canister can fail. This can lead to system pressure loss and the P0442 code. EVAP canisters are an important part of the whole system, meaning if yours goes bad, you’ll need to replace it to prevent the CEL from popping up again on the dash. 

EVAP Solenoid and Hose Damage

Damage to the EVAP solenoid can cause the P0442. These solenoids are low failure parts and usually fail due to accident damage or other mechanical damage.

Although this is not as common as some of the other causes of a P0442 code, because plastic underbody panels usually protect the hose system, it can still occur. This type of damage also makes for a difficult diagnosis as some manufacturers (particularly Toyota) hide the EVAP hoses deep in the car’s bottom.

PCM Flaws 

As this system was only introduced in 1996 and the current system only recently, many cars have faced recalls because of PCMs (power control modules) that pick up false positives from the EVAP system. Some notable ones are the 2014 Ford focus where over 1.3 million vehicles were recalled to fix a canister purge valve issue and all 2014-2015 Jeep Grand Cherokees.

How to Diagnose and Fix the Cause of P0442 Code

Here comes the part that even professional mechanics struggle with. EVAP systems are notoriously finicky, so much as a pinprick leak can cause the P0442 code. On the other hand, you might be able to fix this by tightening the gas cap, so it’s either extremely difficult or not.

ODB II Reader

The first diagnostic step with any check engine light code is to run a full scan using an OBD II scanner. That’s the only way to deduce a P0422 code in the first place. However, with EVAP codes, you can run an ODB II self-test to thoroughly check for leaks. Manufacturers usually lock this feature to professional-grade readers. However, if you have a bidirectional scan tool, you can conduct this test.

All the self-test does is pressurize the system, so that any pressure loss is registered by PCM and shown on the reader. It’s similar to a vacuum test.

EVAP systems are split into two types; early (non-intrusive) and late (intrusive systems). Late or current systems are more sensitive to leaks than early ones, as the PCM plays a more active role in detecting leaks. This information can be found by looking at the technical service bulletin for your vehicle, or in the owner’s manual.

EVAP System Inspection.

The EVAP system is usually well protected from stones and rocks that may damage the EVAP lines. However, any system that uses hoses can be damaged. Check for cracks, holes, or loose hose clamps.

Now, the gas cap is a common cause of the P0442 code. Sometimes it’s not closed properly after filling up the tank, it’s failed or it’s been replaced with a different gas cap. As mentioned before, simply tightening it might solve the issue..

Smoke Machine Test

During any pressure test, it’s important to not crank the tester as high as possible because this will cause air to escape from places that don’t have holes. The EVAP system is a low-pressure system and uses a pressure of about 1 psi.

This is why most auto shops will have a low-pressure tester. Using more pressure than this 1 psi can damage the system and manufacturers will try to prevent you from conducting these tests because most people don’t conduct them correctly.

Most people don’t just have a smoke machine lying around and even though there are DIY methods of making a smoke machine, it may just be less of a pain to get it tested at a shop. If you have one, here’s how to go about testing using it.

There is a specific gas smoke filler cap that allows you to pump smoke into the system and it’s fairly inexpensive. However, this doesn’t allow you to test the gas cap itself, which is a common failure point.

Testing through the purge solenoid allows you to test the whole system. The purge solenoid is on the intake manifold. It’s important to verify that the solenoid itself is not failing, and you can do that using a vacuum tester.

Here, using a purge solenoid adapter can also help prevent pressure loss during the test, but some snug insulation tape can also work.

Make sure you close your vent solenoid before conducting the test, as the smoke will just leak from the vent if it’s not closed. You can do this with an ODB II reader or manually close it by feeding it power.

Hook up your smoke machine to the hose that was attached to the solenoid and run it at 1psi or whatever is the specified pressure for your vehicle. Run a flashlight across the hoses and check for leaks. This method is almost guaranteed to tell you whether you have a P0442 leak.

Does P0442 Clear Itself?

While you can clear the code using an ODB II reader. It should also clear itself in a few drive cycles. The definition of a drive cycle can be different depending on your car’s make and model, but it usually involves driving at a certain speed for a certain duration and stopping a certain amount of times. 

Can you Drive With EVAP Leak?

The EVAP system doesn’t play any significant role in the normal functioning of your vehicle, so you can drive with an EVAP leak, especially a small one. Eventually, the emissions test will roll around and you won’t be able to drive your vehicle, but it’s not a serious issue in terms of vehicle drivability.

Solve P0442 Code Using Quality Parts 

Most modern EVAP systems are sensitive and sometimes require special tools to fix codes such as P0442 or similar. Of course, this applies to issues that aren’t caused by a loose gas cap or a nicked hose. We know that your time is valuable and you want to spend it driving rather than fixing an emissions system issue. 

That’s why here at eEuroparts.com we offer a wide range of EVAP parts for most European vehicles. Just select your vehicle from the dropdown menu, and search for the parts that you need. In return, you’ll get a list of products that are not just made by some of the best brands in the world, but products that are a guaranteed fit for your vehicle.