P144C – Evaporative Emission System Purge Check Valve Performance 

The P144C is an engine code that indicates a problem with the vehicle’s EVAP System. EVAP stands for Evaporative Emission Control System and is one of many emission control systems installed in vehicles.

The main components of the EVAP system are the purge valve, EVAP canister, hoses and vents, leak detection pump, fuel tank, and fuel tank pressure sensor.  Damage or malfunction in any of these components will trigger the P144C – Evaporative Emission System Purge Check Valve Performance error code. Here’s everything you need to know.

What is the EVAP system?

The EVAP system works 24/7, even when the vehicle is switched off, constantly collecting fuel vapors from the fuel system. Unlike exhaust fumes that are released only when the engine is running, gasoline can vaporize even when the engine is off.

Should this vapor escape into the atmosphere, it could cause pollution that is more than that caused by exhaust fumes. Imagine every car on earth releasing fuel vapors into the atmosphere, even while the engine is turned off. To prevent this, the EVAP system monitors and collects the vapor and stores it in the EVAP Canister.

When the engine is switched on, the Canister is purged by opening a valve that allows the stored gasoline vapor to be sucked into the intake manifold. This valve is referred to as the “Purge Valve” and it is one of the most important components of the EVAP system. A faulty purge valve (among other things) will trigger the error code P144C.

Here are some common causes, symptoms, and possible fixes for this problem. 

Potential causes of the P144C error code

P144C error code

Faulty Purge Check Valve

The most common cause of a P144C error code is a faulty purge valve. It is controlled by the electronic control module (ECM) of the vehicle. The purge valve is often closed when the engine is off.

But when the engine is on and warm enough, the valve is opened to let out some of the trapped fuel vapors in the EVAP canister into the engine. Sometimes, the valve could get stuck and does not open or close as it should and it could also be clogged by debris from the canister. Either way, the ECM will detect this abnormality and alert the driver with a check engine light and the P144C error code. 

Damaged or Disconnected Purge Valve Hose

damaged Purge Valve Hose

The purge valve hose performs a similar function as the fuel lines. Only in this case, they convey vapor and not liquid fuel. There is the intake hose which connects the EVAP canister to the purge valve and the outlet hose which connects the purge valve to the engine.

The hose is made of steel or other rigid material capable of withstanding high heat and low pressure. But after considerable usage, the hose could crack, or disconnect from the points of contact. When this happens, there is leakage of gasoline vapor which is detected by ECM as the overall pressure in the EVAP system will drop. The ECM could trigger the DTC P144C code together with the check engine light. 

Vacuum Leaks

For optimal performance, there’s a set amount of air-fuel ratio that enters the engine. This mixture is precise and controlled by the ECM. A vacuum leak occurs when an excess amount of air (more than is required) enters the engine from a source other than the throttle.

This causes the actual amount of air to be higher than what is measured by the engine. Meanwhile, the ECM will inject the right amount of fuel based on the volume of air measured by the mass air flow sensors (which don’t detect the excess airflow) resulting in a lean mix (a mixture with less fuel and excess air). Vacuum leaks can occur when the purge valve hose is damaged or loose, allowing excess air to enter the engine. 

Faulty Fuel Tank Pressure Sensor

Faulty Fuel Tank Pressure Sensor

The fuel tank pressure sensor is located on the fuel tank or inside it and measures the pressure within the fuel tank. The ECM uses the reading from the pressure sensor to determine if there is a leak in the EVAP system. So if the fuel tank sensor is faulty and gives an incorrect reading, this could cause the ECM to incorrectly predict a leak in the system and  trigger a check engine code  

Faulty Leak Detection pump

The leak detection pump (LDP) is responsible for detecting any leakage in the engine, especially within the EVAP system. The LDP increases the pressure within the EVAP system by pumping air into it. This will pressurize the EVAP system and if there is any leakage, the pressure will drop.

The ECM determines the size of the leakage by measuring how fast the pressure drops. A faulty LDP will make it difficult for the ECM to monitor and detect leakages in the system and this could result in a lot of performance and environmental issues. 

Faulty Electronic Control Module (ECM) Programming

The ECM is the control unit of the vehicle. Its duty is to ensure that the engine (and transmission) is operating the way it should. To do this, the ECM constantly runs diagnostic tests on the engine components, one of which is the EVAP system.

faulty Electronic Control Module (ECM)

The ECM regulates the purge valve to open and close, it also controls the leak detection pipe and monitors the fuel tank sensor (and many others)  to get accurate readings on the operating condition of the vehicle. 

Like every computer system, the ECM is programmed to draw inferences and take action based on the information received from the many sensors under its control. If any of these sensors is faulty and sends a wrong reading to the ECM, it could cause the system to malfunction and take inaccurate steps.

Additionally, the ECM can get damaged due to environmental conditions, or a short circuit. If this happens, then it will be unable to diagnose and monitor the engine components successfully creating all manners of problems including a check engine light and an error code. 

Malfunctioning Evaporative Emission (EVAP) System

The EVAP system is a maze of interconnected components designed to function together. Although the system typically requires very little maintenance, any one of its components could fail and cause the entire system to malfunction. I’ve covered most of the components in this section but there are a few others worth mentioning and this includes the gas cap, fuel lines, and EVAP canister. 

The P114C error code can be caused by any of the factors mentioned above and here are some of the symptoms you should watch out for. 

Symptoms Associated with P144C Code 

1. Check engine light on 

The first sign of a problem within the engine compartment of any vehicle is the check engine light. However, the obnoxious yellow (or red) icon alone doesn’t give a lot of information as to what the actual problem is.

This is why it is often accompanied by an error message or a code (or both), in this case, the P144C. It all depends on the model of your vehicle. But if there’s no code or error message displayed on the dashboard, then a quick scan with an OBD II scanner would help to confirm if it is related to the EVAP system or not. 

2. Poor fuel efficiency 

Another symptom associated with the P144C error code is poor fuel efficiency. This would be caused by leakages in the hoses, vents, canister, fuel tank, or fuel lines. When gasoline vapor (that would otherwise have been efficiently used) escapes, fuel consumption increases because more fuel is being used to power the vehicle.

It could also happen when the purge valve is stuck in the open, letting in more than the required amount of fuel vapor into the combustion chamber. This rich mixture (a fuel-air mixture with more than the usual amount of fuel) may burn with more power at the cost of reduced fuel efficiency. 

3. Unusual fuel odors 

If fuel vapors aren’t escaping from damaged components, then excess amounts of the vapor could enter the combustion chamber of the engine. The rich mix that’s formed as a result not only reduces fuel efficiency (as discussed above), but some of the unburned fuel will escape into the exhaust system and then find its way into the environment through the exhaust fumes. You can easily tell by the strong smell of fuel that fills the air when the engine is turned on. 

4. Difficulty starting the engine 

Sometimes you may find it difficult to start your engine. This is another symptom of the P144C code caused by vacuum leaks. As I explained before, when air sips into the combustion chamber from damaged components in the engine, it results in what’s called a lean mix, meaning, more air than fuel in the fuel-air mix.

Consequently, the engine doesn’t have enough fuel to start. You may have to crank the engine several times before it comes to life. 

5. Reduced engine performance 

Apart from the stuttering engine, you may also experience an overall reduction in the performance of your vehicle. Such as misfiring due to sooty spark plugs, less mileage, and rough idling. All this makes for a less-than-smooth driving experience. 

Diagnosing the P144C Code 

As you can see, the P144C code has several possible causes. To fix it, you must know what exactly is causing the problem and that means running some diagnosis. Before I take you walk you through the steps, here are some safety precautions and tools you will need;


  • Make sure your vehicle is turned off
  • When disconnecting the battery terminals start with the negative and then the positive
  • When connecting the battery, connect the positive terminal first and then the negative terminal.
  • Ensure both terminals of the battery do not come in contact with each other.
  • Make sure you use safety glasses and gloves when working on a running engine.
  • Avoid moving parts 


  • A multimeter
  • A set of wrench
  • A screwdriver
  • Safety glasses
  • Gloves
  • An OBD scanner 
  • Your vehicle’s manual

Step-by-step diagnostic procedure 

Inspect purge check valve 

The most common culprit behind the P144C error code is the purge check valve. So its not surprising where the code name – Evaporative Emission System Purge Check Valve Performance – comes from. There are two methods of diagnosing the purge valve; 

Method 1 – Using a Multimeter

In this method, you would need to disconnect the purge valve. This can easily be done by unscrewing the inlet and outlet hose clamps and then disconnecting the purge valve from the power terminal. 

Test 1 – Continuity Test

For this test, you will set the multimeter to the “continuity mode” simply by turning the knob to the sign that looks like a sound wave. After you have done this, connect the power terminals of the purge valve to the two probes from the multimeter. If you hear a beep sound, then the purge valve is in good shape. What this test shows is that the solenoid coil in the purge valve is intact. But if there is no beep sound, that would mean the coil has been damaged.

Test 2 – The resistance test

The resistance test will check to see if the resistance between the positive and negative terminals of the purge valve is at the correct level. To do this, adjust the knob on the multimeter to the resistance “Ohms” sign. Then reconnect the purge valve terminals with the multimeter probes.

This time you should see a reading on the digital display of the multimeter. The expected resistance values are between 14 and 30 Ohms, depending on the model of your car. Anything below or above this range indicates that the purge valve is faulty. 

Method 2 – Power Test

For this test, all you need to do is connect the purge valve terminals directly to the 12 volts battery of your car. It is advisable to disconnect the battery before proceeding. When you attach the terminals of the purge valve to the positive and negative terminals of the battery, you should hear a clicking sound coming from the purge valve. This proves that the valve is opening and closing as it should. But if there is no clicking sound, then the valve is faulty. 

Examine purge valve hoses 

If everything checks out with the purge valve, then begin examining the hoses. This shouldn’t be too difficult since you already have the purge valve disconnected. All you need to do is carefully examine the surface of the inlet and outlet hoses attached to the purge valve. Make sure you check the end of the hose where it attaches to the fuel tank and the engine for pores and cracks that could cause leakage. 

Check for vacuum leaks 

The different ways of locating a vacuum leak one of which is by close inspection. But very tiny cracks and pores can be difficult to locate using this method and in that case, you need to get a little bit creative. Here are some simple and safe ways to do it.

  • You can try listening for high pitch sounds coming from the engine. This is only possible if the leak is outwards. But if the air is being sucked into the engine, then this method will not be very helpful. And sometimes, it could be difficult to hear any noise while the engine is running. So 
  • Lightly spray water on suspected areas. This might sound a bit crude, but hey…if it works, it works, right? All you need is a spray container and some water. Then spray the water along hoses, vents, intake manifold, throttle body, etc. If there is a sudden change in the sound of the engine, then you have just identified the source of the leak. 
  • Use a flammable fluid. This might be a bit too much for some people. But if you are sure you can pull it off, then here you go. All you need is a flammable spray like carburetor cleaner, brake cleaner, or a propane torch. Spray this fluid carefully around suspected areas and listen to the sound of the engine. If there is a sudden change in the RPM, then you have located your leak. Remember not to ignite the propane torch if that is what you intend to use. 
  • Use an EVAP smoker or brake bleeder tool. This requires a bit of technical experience and isn’t for everybody. While brake bleeders are quite common, EVAP smokers aren’t something you’ll have lying around. So at this point, it is best to take your vehicle to a technician to help out. 

Evaluate the fuel tank pressure sensor 

The fuel tank pressure sensor monitors the pressure and vacuum in the EVAP system by giving different voltage signals when there is a change in either pressure or vacuum within the system. To test the sensor, all you need is a multimeter and your vehicle’s manual. First, you must locate the sensor which is in one of two places; either inside the fuel tank or on top of it. 

Once you’ve located it, disconnect the sensor and turn on the ignition switch (only). With this turned on, measure the voltage across the terminals of the fuel tank pressure sensor by connecting the probes of the multimeter to the positive and negative terminals of the sensor. Refer to the manual to see if the values on the multimeter are the same as that in the manual. If it isn’t, then there is a problem with the sensor. 

Assess EVAP system components 

Assessing the state of the EVAP system is done automatically by the vehicle’s Electronic Control Module. However, it can also be assessed by connecting your engine and running diagnostics using an OBD 2 scanner. The tool returns information on the general well-being of the system using codes. The exact code will depend on the model of the car as well as the type of problem detected within the system. A typical example of an EVAP system code is the P144C.

Verify ECM programming

 The ECM is not immune to failure. However, if there is physical damage on the ECM (likely from a short circuit), there would be a corresponding error code displayed on the dashboard. For the P144C error code, the reason for verifying the ECM programming is to ensure that its program is working the way it should. The easiest way to do this is by connecting to a scan tool like the OBD 2 scanner and observing the data PIDS that correspond to the ECM. If the data changes with engine conditions and the values are accurate (when compared to the standard values), then the ECM program is good. Otherwise, you may have to update the ECM program. 

How to Fix the P144C Code 

Knowing the common causes of the P144C code, the fix is quite straightforward. All you need to do is replace or repair the damaged component. The diagnostic process will help you pinpoint the exact component that is defective. Other than the ECM which if not damaged might only require a system update, other components may need to be replaced completely.

This includes damaged purge valve hose and vents, faulty fuel tank pressure sensor, and leak detection pump. Some components like the purge valve can either be replaced or repaired depending on the cause of damage. If the purge valve is still functioning (as determined by the multimeter test), but simply got stuck due to impurities (mainly charcoal from the canister), then it can be cleaned. Once the impurities have been removed, the valve should be good as new. 

Troubleshooting Tips and Common Mistakes 

If you attempted a DIY fix and the P144C code still won’t go away, then check to see that you didn’t make any of these common mistakes. 

Overlooking simple solutions 

Sometimes the biggest mistake is an oversight. Maybe because the solution appears too simple, you tend to neglect it in favor of more complex ones which turn out to be ineffective or more expensive. Whichever is the case, it’s always advisable not to ignore the common signs or simple tests. The fact that a solution appears to be simple doesn’t mean it is ineffective. 

Not testing components before replacement 

Secondly, don’t jump to replacing damaged components. This attitude will cost you a lot of money. Instead, always test a component to ensure that it is faulty and can not be repaired before you opt for replacement. An example is the purge valve. Sometimes the solenoid 

coil is damaged and the valve must be replaced. Other times it could simply get stuck and can be repaired and reused. 

Ignoring other potential causes 

The EVAP system has several components and although the P14C code expressly points to the purge check valve, any of the other components is also a potential cause. So while troubleshooting for the causes of the code, make sure you check out other components. A good place to begin is by following the diagnostic procedure outlined in this article. 

Frequently Asked Questions (FAQ)

How serious is this code? 

The P144C code should not instantly cause panic. That is to say, there is no impending danger of damaging your vehicle if you do not fix the code. However, there are consequences to neglecting the code and this includes erratic engine behavior, poor fuel economy, inconvenience smell of fuel, and the inevitable damage to the environment. 

Can I still drive the car? 

Yes. You can still drive the car but you have to keep in mind the consequences I mentioned above. So even though you can still drive your car, you shouldn’t drive for too long without getting the code fixed. Additionally, you have to consider local emission regulations. In most places, you have to pass an emission test before you are legally able to drive your car. Without the EVAP system, your car emissions will go through the roof and that means a failed emission test. Without passing the test, you won’t be able to legally drive your car.

How can I prevent Future P144C Code Issues? 

Mechanical and electrical devices can’t operate consistently without failing eventually. So yes, the EVAP system and its components will develop faults even with the most diligent maintenance schedule. However, regular maintenance will prolong the life of the system and its components. This will reduce the occurrence of P144C code-related issues. Also, you can monitor the fuel efficiency and other symptoms associated with the P144C code. This attentiveness will help you easily recognize potential causes of false P144C code readings 

When Should I Seek Professional Assistance? 

Issues related to the P144C code can easily be identified and fixed by following the procedures detailed in this article. But certain conditions will necessitate a professional assessment. This includes; persistence of P144C code after attempting repairs on your own, inability to diagnose the issue or a lack of necessary tools or knowledge regarding the process.

How Does the P144C Code Affect Emissions Testing 

Any fault within the EVAP system is guaranteed to affect the emissions test. The reason is that a faulty EVAP system will cause the level of emissions from the engine to be higher than usual. Since the P144C code is directly linked to problems within the EVAP system, it goes without saying that the P144C code

Will heavily impact the outcome of the emissions test. So if you are in a state or region where an emissions test is required for vehicle registration, then you have to ensure proper repairs to fix the P144C code before the test.