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There are over a thousand things that can trigger your car’s “Service Engine Soon” or “Check Engine” light.

One of them is a faulty EVAP system.

On this page, you will find everything you need to know about your car’s EVAP system, including possible causes and solutions to an EVAP leak.

Evaporative (EVAP) System: What is it?

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Most people simply know it as the EVAP system but it’s actually called the Evaporativeission Control System. By definition, it is a closed vehicle system that captures and prevents gas vapors from escaping into the atmosphere.

So why is the EVAP system necessary in vehicles?

Primarily to reduce pollution and enhance the vehicle’s performance. The Environmental Protection Agency (EPA) requires that all vehicles (made from 1996) have this system.

As a fuel, gasoline contains several hydrocarbon elements. The light ones like aromatics, aldehydes, paraffin, and olefins EVAPorate quickly and easily. When they react with air in the presence of sunlight (photochemical reaction) they form a substance called smog. That’s why EVAP tests are also called smog tests.

If not completely sealed, the fuel tank will allow vapors to escape into the atmosphere. That will happen even when you are not driving the vehicle. Meaning your car can pollute for 24 hours a day.

Such uncontrolled EVAP pollution is what is known as an EVAP leak. It can account for up to 20% of a vehicle’s pollution. The EVAP system is what prevents that from happening. More on EVAP leaks a little later, but for now…

Components of an EVAP System

The Evaporative Emission Control System consists of the fuel tank, gas cap, liquid-vapor separator and EVAP canister. The fuel tank holds fuel. It’s usually constructed with some expansion space to allow fuel to expand (on a hot day) without overflowing or leaking.

The gas cap closes the entrance to the fuel tank. For OBD2 vehicles (1996 and newer), it’s usually sealed completely. Such vehicles have venting done through the EVAP canister. On the other hand, OBD1 cars (older than 1996) have a gas cap that has a vacuum/pressure release valve for venting.

The liquid-vapor separator prevents liquid gasoline from getting into the vent line. Ultimately, that ensures that gas doesn’t enter the EVAP canister. If that happens the canister will overload and may leak.

On its part, the EVAP canister traps, and stores fuel vapors. Typically made of steel or plastic, the canister is usually located in the rear quarter panel or the engine compartment. Either way, it’s hidden from view.

Inside the canister is activated charcoal whose purpose is to absorb fuel vapors. The vapors will be stored until you start your vehicle’s engine. Once the vehicle starts running, it will generate some heat. The PCM will then open the canister’s valve and allow the gas vapors to make their way into the engine.

HOW DO YOU KNOW THAT YOU HAVE AN EVAP LEAK?

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Now, back to EVAP leaks.

Although the EVAP system doesn’t require maintenance, it can get faults that turn the Check Engine Light on. The faults typically arise from system weaknesses and/or failures.

Perhaps more interestingly, EVAP leaks don’t usually affect how a car drives. You may only notice or suspect them when the Check Engine Light starts flashing. And that right there is the first sign of an EVAP leak – the Check Engine Light (CEL).

Unfortunately, as mentioned already, there are thousands of other things that can trigger the CEL. So how do you narrow down to an EVAP leak? Some vehicles usually have an accompanying popping sound.

However, that alone will not give you a precise diagnosis; but an EVAP system test will. You can either do a manual test or use a scan tool. Read on to learn how to do EVAP leak diagnoses using both methods.

CAUSES OF AN EVAP LEAK

Knowing the possible causes of an EVAP leak will help you diagnose and fix it better. The common ones include:

• Missing fuel cap
• Loose fuel cap
• Using incorrect fuel cap
• Leaks in the fuel tank
• Leaks in EVAP canister
• Leaking vents and vacuum hoses
• Faulty purge valve. The valve vents fuel vapors to the engine.

WHY YOU SHOULD NEVER DRIVE WITH AN EVAP LEAK

It is possible to drive a vehicle that has an EVAP leak. But you should avoid that as much as possible. Why? For starters, it will pollute the environment.
Secondly, your vehicle will not pass state and/or federal emission tests. That’s a traffic offense by its own merits.

Thirdly, the vehicle’s performance may be affected. While driving won’t be an issue, it may take longer to start and may record lower fuel mileage. In short, you risk spending more on gas.

HOW TO DIAGNOSE EVAP LEAKS

There are two ways of diagnosing EVAP leaks. The first is using manual tests and the second involves using a scan tool.

How to Manual Test

Start by visually inspecting the gas cap, fuel tank, EVAP canister, vapor lines, and filler neck for leaks. Make sure the vehicle is not running and the vent solenoids are closed.

Proceed to examine the pressure in the fuel pressure sensor. With the vent valve and purge valve closed, watch how the pressure changes.

If it drops then you have an EVAP leak, but if it doesn’t it means your EVAP system is working perfectly.

How to Test EVAP Leak with a Scan Tool

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Bonus: NEXPEAK NX501: I/M Readiness O2 Evap OBD2 Scanner with Mode 6 Review

A more straightforward way of testing for EVAP leaks is by using a scan tool. In addition to other functions, OBD2 scanners check EVAP systems to ensure that hydrocarbons don’t escape into the atmosphere.

Usually, OBD EVAP monitors run once for every drive cycle when the fuel tank is between 15 and 85% full.

They use sensors known as “purge flow sensors” to identify even the smallest of leaks. If there’s a leak, the scanner will tell you by displaying a fault code.

EVAP fault codes range from P0440 to P0457. Here is what each one of them means:

Code Meaning

P0440 Faulty evaporative emission control system
P0441 Incorrect purge flow in the evaporative emission control system
P0442 Small leak in EVAP emission control system
P0443 Purge control valve circuit in EVAP emission control system
P0444 Control valve circuit is open
P0445 Short in control valve circuit
P0446 Evaporative emission control system vent control circuit
P0447 Evap emission control system vent control circuit is open
P0448 Short in EVAP emission control system vent control circuit
P0449 EVAP emission control system vent valve/solenoid circuit
P0450 Evaporative emission control system pressure sensor
P0451 EVAP emission control system pressure sensor
P0452 Low input in EVAP emission control system pressure sensor
P0453 High input in EVAP emission control system pressure sensor
P0454 Intermittent EVAP emission control system pressure sensor
P0455 Gross leak in EVAP emission control system
P0456 Small leak in EVAP emission control system
P0457 Fuel cap leak in EVAP emission control system

WHAT TO DO WITH AN EVAP LEAK?

Not all EVAP leaks are equal. While some require a big budget and professional repair, others are easily fixable. For instance, if you run into P0440, P0455 and/or P0457 fault codes, simply check that the gas cap is tightly in place and that there’s no debris or damage in the filler tank inlet. If after doing that the code still persists, consider replacing the gas cap altogether.

The one code you don’t want is the P0442. It indicates that the EVAP system has a leak. Besides being hard to find, the EVAP leak will require a professional auto mechanic to fix. And if it’s the EVAP canister that’s damaged it may require replacement (depending on the extent of the damage).
Generally, the average cost of a new canister ranges from $260 to $430 (exclusive of labor costs). Luckily you can avoid such expenses easily just by not overfilling the fuel tank.

THE BOTTOM LINE

Keeping your EVAP system in check will go a long way in ensuring that there are no EVAP leaks. Remember that an EVAP leak not only leads to pollution but your car will not pass a smog test. That’s why you need to run EVAP system checks as frequently as possible.

You can do that manually or use a scan tool. The latter is more reliable since it’s easier and accurate. Just make sure you know how to pull and interpret the codes. Feel free to refer to the table above for what each code means.

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Over 50 percent of smog or emission test failures are caused by malfunctioned o2 sensors. A bad oxygen sensor can literally drain your pocket due to the negative impact it can have on your vehicle. Therefore, it is vital that you know how to test your oxygen sensor to determine whether it is working well or is faulty.

O2 sensor: What is it for?

An oxygen sensor is located in the exhaust stream. It is used to monitor in real time the ratio of air/fuel to determine whether it is lean or rich. This is done by measuring the amount of oxygen in the liquid or gas passing through the exhaust manifold.

Many people misunderstand the measuring process. The sensor does not measure the concentration of oxygen. Rather, it measures the difference between oxygen in the air and oxygen in the exhaust gas.

Apart from determining the air/fuel ratio, an o2 sensor can also determine whether the catalytic converter is working well. The sensor can adjust the air/fuel ratio to ensure the catalytic converter is working efficiently.

Once the ratio is determined, a voltage is created and it flows through the o2 sensor, sending the reading to the CPU. The CPU then adjusts the ratio according to what is appropriate. This reduces exhaust emissions thus contributing to a healthier environment.

Tampering with the o2 sensor signal could negatively affect emissions control since it controls emissions. Additionally, it can also cause damage to the vehicle. For example, a faulty o2 sensor can damage the catalytic converter.

Types of o2 Sensors

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Oxygen sensors can either be heated or unheated. However, in modern times, heated oxygen sensors are more common in vehicles.

Unheated oxygen sensors are found in old vehicles, up to the 1990 models. These sensors need to be replaced more often compared to heated oxygen sensors. It is advised that the sensors be replaced after every 30,000 to 50,000 miles.

Heated oxygen sensors are found in modern vehicles, from the 1990 models up to present. These sensors are more durable and should be replaced after every 60,000 to 90,000 miles.

Since oxygen sensors are exposed to harsh conditions, they should be replaced at the appropriate time to avoid problems.

Bad o2 Sensor Symptoms

There are various signs that hint your vehicle has a problem with its oxygen sensor. Some of these signs include:

1) Foul Exhaust Odor

When the o2 sensor has malfunctioned, a strong, unpleasant odor will emanate from the exhaust. If the problem is not dealt with immediately, the smell could even spread to the vehicle’s interior. This would be such an embarrassing situation.

2) The Check Engine Light is On

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The Check Engine Light is an indication that there is a problem with the vehicle. Although it does not specifically mean that the problem lies with the oxygen sensor, there is a possibility the o2 sensor has a problem. Always get your vehicle checked immediately you notice the light is on.

3) Decreased Vehicle Performance

Your vehicle will generally reduce its performance in various areas. You may experience engine stalling and weak acceleration. Additionally, you may notice the engine runs roughly or irregularly even when it is idle.

4) Bad Gas Mileage

Have you noticed you fill up your gas tank more often than you usually do? This may be due to bad gas mileage. When the oxygen sensor fails to work effectively, the mixture of fuel and air will be rich.

A rich mixture of fuel and air means more gas is consumed during the process of internal combustion. This means a higher fuel consumption of gas and digging deeper into your pockets.

How to Test o2 Sensor Using an ODB2 Scan Tool

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Bonus: NEXPEAK NX501: O2 Evap I/M Readiness OBD2 Scanner with Mode 6 Review 

Step 1:

Insert the OBD2 scan tool connector to the diagnostic link connector (DLC) on your vehicle. The DLC has 16 pins and is shaped almost like a triangle. If you cannot find it, you can search for its location using your web browser and ensure you have specified your car’s model.

Step 2:

Turn on your vehicle’s engine so that the scanner can communicate with the vehicle’s onboard system. Ensure you do not start the car’s engine, only turn on the ignition. If the scanner is blank after doing this, try reconnecting it or shaking it a bit.

In some scanners, you will be required to key in your vehicle’s identification number. Additionally, you may be prompted to key in the vehicle’s make and model. This process may not be present in some scanners.

Step 3:

After the scanner boots, go to the menu and select ‘Trouble Codes’ or ‘Codes’.

Step 4:

Choose the system you would like to troubleshoot. 2 or more codes will appear on your screen after this process.

The codes that appear can either be Pending codes or Active codes. These are the most common types of codes. However, there are other types of codes.

Active codes are also known as live codes and they keep the Check Engine Light on. They imply there is a problem with the system and it needs to be solved.

Pending codes indicate a pending problem. It shows that the operation of an emission control system failed once and if it fails again the Check Engine Light will be turned on. Once it is turned on, the pending code becomes an active code.

Step 5:

Interpret the code. The OBD2 scan tool will diagnose the problem and reveal it in code. If you are not familiar with interpreting these codes, you can search for them on the internet. While on the internet, you can also search for how to interpret various codes so that it becomes easier the next time you are using the OBD2 scan tool.

THE BOTTOM LINE

Never ignore any signs of failure of the oxygen sensor. The earlier the problem is diagnosed the better.

Solving o2 sensor problems early will enable you to save financially since little to no damage would have been done to the vehicle. Additionally, you will save on the amount of gas you use while driving.

If you find it difficult to use the OBD scan tool, take your car to a good mechanic to check it out.

Worried about the security of your car? Are you afraid that someone might get away with your automobile?

Worry not!

With the help of Engine Immobilizers, you can keep your car safe, secure and prevent it from being stolen. Usually, the car thieves steal cars by connecting the ignition wires of the vehicles, i.e. by hot-wiring it. With the help of an Engine Immobilizer, even if the ignition wires are connected, the car’s engine will not start up.

What is an Engine Immobilizer?

Engine Immobilizer is an anti-theft system which keeps your car safe from prowlers and car thieves. When you put your car key inside the ignition switch, it transmits a code to your automobile. There is a code that is present on the transponder chip. If it matches the code present inside your car’s Engine Immobilizer, only then would your car start.

The Engine Immobilizer stops your car’s engine from being started unless the matching digital is present. Only the car’s matching key would start the car’s engine. With any other incorrect car key, the engine of your car will not work. Even if the thieves are inside your car, they will not be able to just hotwire your car.

Engine Immobilizers are basically anti-theft devices which are found inside your cars. Countries such as Germany and the United Kingdom have a law which makes the installation of Immobilizers in cars mandatory. Since the Engine Immobilizer works automatically, you do not have to activate it first to make sure your car is safe. With the use of the Engine Immobilizer, the rate of car theft has been reduced by almost 40%!

Do I have an Engine Immobilizer?

We have learned what an Engine Immobilizer is. The question which arises is whether your car comes with an Engine Immobilizer or not.

It can be a real stump if you think that your car is fitted with an Engine Immobilizer and then later find out that you were wrong.
All the cars that have been manufactured since 1998 have a mandatory clause to include an Engine Immobilizer in them.

Unless the Engine immobilizer has been disabled or removed, it is most likely that you have an Engine Immobilizer if the car was built after 1998. If your car was built before 1998, there might still be a chance that it comes with a factory-fitted immobilizer. You should check the car’s user and owner manual to make sure that you do.

How does an Engine Immobilizer work in a car?

There are three main systems which make your car move. These are as follows:
• The Ignition System
• The Fuel System
• The Starter Motor

Immobilizers disable two out of these three systems and stop your car from being started. There is a transponder in the key of your car. When you put the car key in the ignition, a code is transmitted from the transponder chip inside the key to the Electronic Control Unit of your automobile.

This is done usually through a receiver present inside the steering wheel of the car. The method may differ from manufacturer to manufacturer, but the basic working principle in every one of them is the same.

The mechanisms of the Engine Immobilizer may change, but their function is to keep your car theft-free.

How the Engine Immobilizers work technically isn’t a fact that is publicized. This is because it might help the thieves in coming up with a counter-strategy. This is how an Engine Immobilizer generally works.

The two components through which an Engine Immobilizer works are:

• A transponder in the car key
• A radio frequency reader

The transponder is present inside the car key. The radio frequency reader is mostly present inside the steering wheel. When the key is placed inside the ignition, the transponder sends a signal to the radio frequency reader.

This signal is a unique code which identifies whether the correct key is placed. If it is the right key, the ECU will allow the car to be started. Otherwise, two of the three main car starting systems are disabled, and the vehicle doesn’t start up.

Is it worth having one?

Your car is safer from thieves if you have an Engine Immobilizer. It is always better to be safe than sorry. While an Engine Immobilizer may not be the only option for the security of your car, it is the most easily accessible one. You can also keep your car safe by using steering wheel locks etc.

Bonus: Autel MaxiCOM MK808: IMMO OBD2 Automotive Diagnostic Tool Review