P0456 Jeep Code: Meaning & Symptoms (How to Fix)

A P0456 Jeep code is an error most car owners wouldn’t mind having. After all, it has very low severity and doesn’t negatively impact the vehicle’s drivability. However, this is a flawed mindset. When left unattended, a P0456 Jeep code can lead to compounded performance issues and huge repair expenses. That said, it is best to pick up on its symptoms early on.

P0456 Jeep code symptoms include:

• A triggered Check Engine Light
• Starting difficulties
• Fuel odors in your cabin
• Reduced fuel economy

While these indicators typically point to an EVAP system leak, they can be caused by an ill-fitted gas cap and easily fixed by replacing the faulty component.

Noticing these symptoms and correctly diagnosing them can prove intricate. This guide will cover probable causes and telltale signs of a P0456 Jeep code, as well as associated costs and tips on how to fix them.

The Meaning of the P0456 Jeep Code

The P0456 Jeep code is one of several error codes saved in your car’s onboard computer system and read through a 16-pin OBD-II diagnostic connector. It is defined as “Evaporative Emission System – Small Leak Detected,” which is similar to the following error codes:

• P0457: Evaporative Emission System – Leak Detected
• P0455: System Gross Leak Evaporative Emission
• P0442: Evaporative Emission System – Leak Detected (Small Leak)

This definition is quite self-explanatory, as it means a small leak in your vehicle’s Evaporative Emission Control or EVAP system (smaller than 0.020 inches in diameter). While describing this code is a piece of cake, finding the source of the leak that sets this code off is an altogether different story – something that requires a working knowledge of your car’s emission control system.

Understanding the EVAP System

The Evaporative Emission Control System or EVAP consists of the fuel tank, valves, hoses, charcoal canister, and fuel tank gas cap. Its primary responsibility is to stop unfiltered gasoline fumes inside your car from leaking into the atmosphere.

It also has pressure sensors, purge control solenoids, and a vacuum system that gets things moving along. These components work tirelessly while you drive and as your car sits in the garage.

Your vehicle’s EVAP system not only functions as a pollution control feature but also keeps dangerous fumes from seeping into your cabin. Customarily, this complex network transport vapors from the fuel system to the charcoal canister and from the charcoal canister back to the engine for burning – provided no part of the system is compromised.

The PCM (a.k.a. your vehicle’s brain) does regular checks with help from the LDP (Leak Detection Pump) to ensure this is the case and that the EVAP system causes neither fire nor explosion hazards.

The Role of Your PCM

As established, the PCM is what carries out your car’s self-diagnostics by checking for electrical and mechanical faults. After which, it works with the leak detection system to test for leaks and blockages by sealing the vent valves and pressurizing the EVAP system.

These steps enable both the PCM and LDP to detect the presence and size of a leak. And when this discrepancy happens at least twice consecutively, your dash panel illuminates the ‘Check Engine Light’ and displays the code P0456.

Common P0456 DTC Code Symptoms

Here are other symptoms that signify a probable leak in your car’s EVAP system:

• Illuminated ‘Check Engine Light’ or ‘Service Engine Soon’ warning light – This indicator is the most common and is expected to occur once your vehicle’s PCM detects an EVAP system leak.
• A failed emissions test is the 2nd most common symptom and sometimes happens before a vehicle owner gets the P0456 code on his dash panel.
• Rough ride quality – More of an outcome than a symptom, this is usually the result of a failing or malfunctioning EVAP charcoal canister valve (a.k.a. purge solenoid). You may notice your vehicle running inconsistently (often at a stop or while driving at low speeds).
• Stalling/no-start issues – It is a given that the EVAP system controls vapor. If a leak within the system is left sitting or damage to the purge solenoid continues, it can impact how efficiently your car starts and runs. Ultimately, any form of interruption to your vehicle’s internal combustion may cause the engine to stall out completely or refuse to start altogether.
• Fuel/gasoline smell – Although more commonly associated with larger leaks, this indicator usually manifests when an EVAP system leak has been around for a while. Only then will the smell of gasoline become apparent.
• Decreased fuel efficiency – Out of all the signs, this is the most difficult to notice since the leaks that set off the P0456 Jeep code are so minor that their bearing on fuel efficiency is close to negligible.

Possible Causes of the P0456 Jeep Code

A triggered CEL and display of the P0456 fault code rarely result from a glitch, meaning that these indicators (though not considered serious) should be addressed immediately. It may only pertain to a small leak. But there are multiple areas in your vehicle’s EVAP system where leakage could occur.

That said, I highly advise looking into the following potential culprits at the first sign of this problem:

• Malfunctioning gas cap or purge vent valve
• Misplaced/loose gas cap
• Damaged fuel filler tube or gas cap O-ring
• Obstruction in the fuel filler cap
• Incorrect gas cap used
• Leak in the fuel tank or EVAP canister
• Leaking or disconnected EVAP hose
• Leaking/damaged charcoal canister
• Defective canister valve
• Vacuum feed line or control valve leaks
• Faulty FTP sensor or Leak Detection Pump

While you can still drive with a Jeep code P0456, it is not wise to do so until you have addressed its problem source. If you let the issue sit unattended, your vehicle will continue to emit toxic fumes harmful to the environment.

You will also eventually fail emissions testing, which is critical to renewing vehicle registration. Lastly, a compromised EVAP system will adversely impact the atmosphere and your car’s gas mileage.

Cost of Fixing a P0456 Jeep Code

Having a ‘Check Engine Light Diagnostic’ run to determine what is setting off the P0456 code for your Jeep Wrangler could cost anywhere between $95 and $110 (sans labor).

While relatively lower than other vehicle makes/models (for instance, a BMW with an estimated cost of $124.99), this price can still go up depending on your Jeep’s engine (and whether it is modded) and if other fault codes accompany the P0456 code.

As for labor costs, most auto shops charge a minimum of $100 or $35 – $150 per hour.

EVAP System Repairs

EVAP Component	Estimated Cost
Gas Cap O-ring	$10 – $50
Gas/Fuel Filler Cap	$20 – $80
EVAP Line Replacement	$50 – $100
Purge Volume Control Valve	$150 – $200
Charcoal Canister Vent Control Valve	$150 – $200
EVAP Canister/Hose	$190 – $600
Charcoal Canister	$200 – $600
Fuel Filler Tube/Neck/Inlet	$200 – $850
Vacuum Feed Line	$100 – $1,000
Fuel Tank	$400 – $1,100

For each of the above repairs, the estimated cost includes relevant parts and the labor cost required for the repair (but exclusive of taxes and fees). If a replacement part is warranted, costs will fluctuate depending on whether you prefer an OEM or aftermarket product. But ultimately, your total spend relies heavily on the location of the leakage and its cause.

How to Diagnose the P0456 Jeep Code

1. Scan and Fix Other Fault Codes

Scan your Jeep with an OBD-II Scanner like an Autel Maxicom MK908P Scanner (view on Amazon) to verify if any other fault code does not accompany the P0456 code. If it does, make sure to repair and diagnose the other error codes first to get them out of the way.

Do not forget to document your findings as you do this step. Mechanics usually use freeze-frame data to verify the fault code’s time of occurrence.

Tip: A P0441, P0440, or P0446 would most likely pertain to a solenoid failure, leaking charcoal canister, or a more complicated EVAP system leak.

2. Inspect Fuel Tank Gas Cap

Inspect your fuel tank gas cap, and tighten it if it is loose to clear the code. If damaged/deteriorated, replace it immediately and see if the fault code persists. Make sure to include gas cap O-rings in your inspection. If in doubt regarding the integrity of your gas cap, get a replacement anyway.

3. Check for Leaks

Check for any visible leaks. If none, proceed with inspecting EVAP hoses connected to the engine air box if cracked or disconnected.

Tip: Using an EVAP smoke machine to spot leaks around the vacuum hoses and in the fuel tank is highly-effective and strongly advised. You can purchase your own EVAP smoke tester like ANCEL S3000 Automotive EVAP Smoke Machine Leak Detector (view on Amazon) online or visit a local auto shop if you do not have one.

4. Inspect Fuel Tank and Charcoal Canister

Do the same level of inspection for the fuel tank and charcoal canister and replace damaged parts as needed.

5. Check Purge Valve Vent

If there is no leak or visible damage, check your vehicle’s purge valve vent for blockage from dirt, debris, or other kinds of obstruction such as spider webs. No matter how seemingly negligible an obstruction is, it could still prevent a total vapor seal in the purge control valve (usually found under the hood, near the intake manifold or airbox).

6. Check Purge Volume Control Valve

Once you have made sure it is blockage-free, check the purge volume control valve to see if it operates according to spec. Test by removing hoses from both sides and blowing through the openings while no power is supplied to the valve. If the valves are sealing properly, you should not be able to blow through them. Otherwise, the purge control valve may have gotten sticky and developed a small leak.

7. Test the Charcoal Canister Vent Valve

Locate the charcoal canister vent valve (usually connected to the charcoal canister underneath the car) and test it the same way. But this time, see if air passes through the openings when you blow through it (note that there should be no power applied to the valve during this test). If it does, the canister is operating properly.

You can also test the valve another way by supplying a fused power source to one side and grounding to the electrical connector on the other. With this second approach, no air should pass through (same as the purge volume control valve test). If you send both 12V+ and ground to it, the valve should close and open-air through it during the process. Otherwise, the charcoal canister vent valve is faulty and needs to be replaced.

8. Seek Assistance

You may eventually have to seek assistance from a seasoned mechanic for tiny EVAP leaks, as they are challenging to find (even when using a smoke machine). Sure, it would be nice to locate and fix them yourself just by performing initial diagnostics and replacing defective parts. But if things boil down to outsourcing the task to a professional, do not feel bad if you do so.

Common Mistakes During Diagnosis

• Assuming the gas cap or purge control valve is the culprit without doing a thorough, complete system diagnostics
• Jumping to advanced troubleshooting straight away without considering driver negligence
• Not checking if any wiring connected to the EVAP system is broken or cut
• Replacing components without verifying first that they are indeed the problem
• Not looking up TSBs or Technical Service Bulletins related to fixing the code resulting in misdiagnosis

It is a given that the P0456 Jeep code (including what shows up on the Jeep Grand Cherokee) is a bit tricky to diagnose. That said, you should first inspect the gas cap, vent valves, and the underside of your vehicle.

Once you have ascertained there is neither negligence on your part nor physical damage to any of the exposed components, then that will be the best time to proceed with a full-blown CEL diagnostics and EVAP system check.

Fixes to Small EVAP Leaks

After identifying its potential causes, it is only right to look into ways to clear the P0456 Jeep code. After all, we would not want to allow fuel vapors (a.k.a. hydrocarbons) to escape into the environment as pollutants. One of the below fixes is bound to resolve the issue, especially if the identified problem source is not too complicated:

• Tightening a loose gas cap (or making sure you are using the right one)
• Getting a new fuel tank gas cap or O-ring
• Ridding the fuel filler cap and inlet of blockage
• Replacing the leaking/plugged purge vent valve
• Changing the purge control valve or EVAP hose
• Swapping out damaged vacuum feed lines
• Repairing damaged wiring/connectors

This list is non-exhaustive, as it does not cover complex leaks. A compromised EVAP system that traces back to a bad charcoal canister, leaking fuel tank, or defective LDP and FTP sensor is also not included in the remedies above since it entails more than just minor repairs and parts replacement to be resolved.

In the event of complications stemming from a P0456 code, a professional mechanic should be able to give you a quote on what else needs to be repaired and their corresponding costs.

Conclusion – Fixing the P0456 Jeep Code

It is quite surprising that the P0456 code is not that common for most vehicles. Some OEMs do not even have the said error code in their DTCs or Diagnostic Trouble Codes list. However, it is not something to be procrastinated on, as your Jeep needs to adhere to emissions guidelines if it were ever to put its wheels on the road.

Jeep aficionados understand that resolving this fault code can be pretty pesky because of how small the leak can be (making it difficult to locate in your car’s fuel vapor system). It also does not help that your PCM only runs an EVAP leak test when your fuel level is between 15% and 85%.

Still, their advice is to address the P0456 Jeep code immediately. Doing so will lead to cleaner emissions and spell the difference between a minor repair and spending big bucks on a major overhaul.