How to Troubleshoot & Fix P0440 Jeep Grand Cherokee DTC Code?

As a Jeep Grand Cherokee owner, you might often face several error codes, such as P0440, P1391, P0172, P0300, etc. Among them, the Grand Cherokee shows a P0440 code when its Powertrain Control Module (PCM) detects a fault with the EVAP system. 

Though it seems like a minor issue, it can cause major problems and costly fines. So, continue reading this article to learn why this code arises and how to troubleshoot and solve it. 

What Does P0440 Jeep Grand Cherokee Code Mean?

P0440 is an OBD-II generic trouble code that indicates a malfunction with a Jeep Grand Cherokee’s Evaporative Emission Control System (EVAP). It’s a universal OBD-II fault code. 

This explains that the P0440 code will indicate the same thing regardless of the manufacturer or model of the Jeep.

Here, the Evaporative Emission Control System (EVAP) is a device used in modern gasoline-powered Jeeps to stop gasoline vapors from leaving the fuel tank or fuel system and polluting the atmosphere. 

According to the Environmental Protection Agency (EPA), high temperatures cause two-wheelers to lose between 2% and 5% of their fuel. So, since the 1970s, gasoline-powered automobiles have been required to include EVAP systems. 

The market for automotive Evaporative Emission Control Systems (EVAP) was valued at USD 46 billion in 2018 and is anticipated to grow at a 5.5% CAGR between 2019 and 2025. 

P0440 is typically not an imminent risk to your Grand Cherokee’s driveability. Still, it is best to get it identified and fixed as soon as possible. Because if you wait, you could face a whole variety of issues to deal with. 

If we break down the code, we get the following:

• P = Stands for powertrain
• 0 = Generic ODB code, also known as Standardized (SAE) code.
• 4 = Auxiliary emission controls 
• 40 = Specific fault index. In our case, It indicates Evaporative Emission Control (EVAP) System issue.

P0440 Code: What Causes Evaporative Emission Control (EVAP) System Issue on Jeep Grand Cherokee?

To prohibit fuel vapors from readily escaping into the environment, the Environmental Protection Agency and California Air Resources Board have established evaporative emission guidelines. 

Almost all of the major automakers, including Toyota, Jeep, Chevrolet, Ford, Honda, and others, have their own EVAP system that is made exclusively for their vehicles. 

However, this EVAP system can malfunction for a number of reasons, just like any other component. Among them are:

1. Canister problems
2. Faulty fuel cap
3. Faulty canister purge valve
4. Malfunctioning vacuum switch
5. Leaks
6. Malfunctioning EVAP system pressure sensor
7. Problems with the vent control valve

Read Also: How To Troubleshoot & Fix P1391 Jeep Code? Detailed Guideline!

How to Troubleshoot & Fix P0440 Jeep Grand Cherokee Code?

It might be difficult to accurately pinpoint an issue with the EVAP system. The vehicle board’s low computer capacity, wide operating area, and restricted measuring capabilities are the major causes of this.

But, if you have some idea how this EVAP system works and its several parts, you can easily troubleshoot and fix the P0440 Jeep Grand Cherokee Code. So, follow the below-mentioned procedure carefully: 

1. Inspect the Fuel Cap

Examining the gas cap is the initial step in troubleshooting the P0440 error. At first glance, this might not appear important, but the whole fuel system could be exposed to dust and dirt without an air-tight seal. 

A faulty fuel cap symptoms include

• Various trouble codes relating to emissions.
• Gasoline odor coming from the Jeep’s outside.
• Poor fuel efficiency.
• Engine-light indicator.

To solve this, you have to tighten the fuel cap perfectly. If you lose it or break it, install a new one, which might cost you around $90 to $110. 

2. Check the Canister

If you follow step #1 but still get the P0440 error number, there could be a problem with the charcoal canister. 

On a Jeep Cherokee, this canister is situated above the muffler’s back. Here are several signs that the EVAP system’s canister is malfunctioning:

• Poor fuel efficiency.
• Emissions test failure.
• Excess smoke from the exhaust.
• Strong petrol smell
• Check the engine light on.
• Decreased vehicle performance.
• When you open the gasoline tank cap, there may be pinging or hissing sounds.

It is necessary to repair an EVAP canister if it is not operating properly. Replacement costs might range from $300 to $400.

Here you can also bypass canister lines. Although bypassing an EVAP canister is not recommended, you can do it in an emergency.

Read Also: How To Troubleshoot & Fix P2173 Jeep Compass Code?

3. Check the Canister Purge Valve

If the canister is discovered to be in good condition, you must look at the purge valve to find a problem. The most typical purge valve problems occur when they are stuck in open or closed positions or fail to operate at the right time.

Symptoms of a faulty canister purge valve:

• The jeep is not starting.
• Reduced gas mileage.
• Engine issues.
• The check engine light illuminates.
• Rough idle.
• Engine performance issues.
• Failing the emissions test.

If you notice that the Purge Valve becomes faulty, you must have to replace it.

Here is a step-by-step procedure on how to replace the canister Purge valve/solenoid:

• Step 1: First, unplug the Jeep’s battery and lift the hood to find the canister purge solenoid.
• Step 2: Once you’ve found it, remove the electrical wiring connected to it. After that, disconnect the vacuum tubes.
• Step 3: Remove the old canister purge solenoid by removing the bolt which holds it in place. Then replace it with a new one and redo the previous processes to set it up.
• Step 4: Finally, reconnect the battery wires, turn on the engine, and then look for any trouble codes.

You might need to spend nearly $100 to finish this replacement process. P0440 Code ought to be gone at this point. If not, proceed to the following troubleshooting.

4. Check for any Leaks (which include: the vacuum, fuel tank, vapor lines, and purge valve):

Though it may appear to be a minor issue, a leak in the EVAP system might result in the P0440 code. And the vacuum, fuel tank, vapor lines, and purge valve are ideal places to start looking for leaks.

Here are the steps to detect leaks in the vacuum, fuel tank, vapor lines, and purge valve:

Vacuum Leaks

To test for leaks, attach a vacuum gauge to the vacuum pipe and turn on the vehicle. If it is okay, the gauge will show a consistent vacuum pressure. But, if there is a leak, you’ll get fluctuating results from the gauge.

Symptoms of vacuum leaks:

• Rough engine operation or stalling
• Trouble starting the Jeep’s engine.
• Too much or too little engine idle

Vapor Line Leaks

By using a smoke machine, you can quickly detect any vapor line leaks. This device basically releases smoke into the system to help detect leaks more easily.

Symptoms of vapor line leaks:

• Lower fuel efficiency.
• Check engine warning light is on.
• Fuel odor either outside or inside the Jeep.

Fuel Tank Leaks

A pressure tester can be used to find a fuel tank leak. By applying pressure to the gasoline tank, this pressure tester searches for leaks. Checking the gasoline tank for rust or damage might also help you locate a leak.

Symptoms of fuel tank leaks:

• Unexpectedly low fuel gauge reading.
• Inside or outside the Jeep, there is a fuel odor.
• Visible petrol marks on the ground beneath the Jeep.

Purge Valve Leaks

To find any leaks, examine the purge valve for any indications of corrosion or debris. It can also be identified by measuring the system’s vacuum pressure. Vacuum pressure fluctuations might be an indication of a purge valve leak.

Symptoms of purge valve leaks:

• Trouble starting the Jeep’s engine.
• Rough or halting engine operation.
• Check engine warning light is on.

If you detect leaks from any of these, you have to repair them. Here, you should consult an expert mechanic. This may cost you between $100 to $200.

Read Also: How to Troubleshoot & Fix P2173 Jeep Patriot Code?

5. Check the EVAP System Pressure Sensor

There’s a high possibility that the EVAP system pressure sensor is malfunctioning if you’re still unable to resolve the P0440 error. Therefore, you must test the sensor in order to identify any problems.

A pressure tester or a vacuum gauge can be used for the task. Simply attach the vacuum hose to the gauge or tester, then turn the engine on. 

If this sensor is okay, you’ll get consistent vacuum pressure. But, if it does not meet the ideal readings, there might be an issue with the pressure sensor.

In this situation, you have to replace it. This might cost you around $150 to $250.

This video might help you to test and replace it:

6. Check the Vent Control Valve

If all of the above elements are in good working order, examine the vent control valve. This valve is typically situated near the gasoline tank.

When the pressure within the tank hits a specific level, this allows air to go into the tank. This valve may become stuck, develop debris buildup, or have internal solenoid failure and stop working.

Test it using PGM Tester

To check any leaks, PGM Tester provides the vent valve with 12 volts. A flawless valve will create a click sound, and the openings shouldn’t allow air to pass through. 

However, if the air blows through the valve while it is turned on, it is defective and needs to be replaced.

To replace it, consult with an expert mechanic. This valve replacement might cost you between $100 and $200.

To test and replace it, you can take help from this video:

Read Also: How to Troubleshoot & Fix U1504 Jeep Cherokee Code?

FAQs.

You could still have questions even after reading this article. To understand more, go through these commonly asked questions. We did our best to respond properly to these inquiries.

Conclusion

By following all the troubleshooting methods mentioned above, it’s sure that your Jeep Grand Cherokee’s P0440 Code will disappear. You can fix some of these issues on your own, but for others, a qualified technician is required. 

Finally, always look for any symptoms mentioned above and take immediate action if you find any. Because any minor issues might lead to a major one. So, don’t neglect any of them.

Read Also: How to Troubleshoot & Fix P0038 Jeep Code? (In-Depth Guide)