Code P0455 is a fault code usually found in sedans, SUVs, and even luxury vehicles. Many drivers often dismiss it due to its low drivability impact. However, it would be unwise to avoid it. An unattended EVAP leak can lead to hefty repair costs and poor vehicle performance.
The P0455 Jeep code occurs when the PCM detects a large EVAP leak. Symptoms include an illuminated CEL, subpar engine performance, stalling, and excessive exhaust smoke (among others). A malfunctioning gas cap or a defective emissions control system component can cause the fault code.
However, the list does not end there. More serious faults, such as a defective Leak Detection Pump or FTP sensor, sticky purge valve solenoid, or a failing PCM, can also give rise to this trouble code.
Continue reading this article if you want to learn more about the causes and symptoms of a P0455 Jeep code and how to resolve them.
What the P0455 Code Means
Diagnostic Trouble Code P0455 is an error concerning an issue with your vehicle’s emission control system. It means “Evaporative Emission Control System (EVAP) – Gross/Large Leak Detected,” read via an OBD-II diagnostic scan tool.
Similar to DTC P0456, code P0455 is quite self-explanatory and does not only relate to Jeeps (despite being referred to as Jeep code P0455 by most vehicle owners).
This fault code reads differently, depending on a car’s year, make, and model. Here are some examples of how the P0455 code displays in the OBD-II scanner for the following vehicles:
|Error Code Reading
|EVAP System Gross Leak Detected
|Evaporative Emission Control System Leak Detected Gross Leak
|P0455 Jeep Grand Cherokee
|EVAP System – Leak Detected (Large)
|EVAP Emission System Leak Detected Large Leak
As mentioned in an earlier article on Jeep code P0456, the EVAP system mitigates toxic exhaust fumes released into the atmosphere. However, it can only do so if its main and supplementary components are damage-free and in good working conditions. These components include:
- Fuel tank
- Charcoal canister (view on Amazon)
- Fuel tank gas cap
- Pressure sensors
- Purge control solenoids
- Vacuum system
Your car’s PCM employs its own self-diagnostics and the LDP (Leak Detection Pump) to ensure that this is the case. Once it detects a sizeable leak in the EVAP system, the PCM automatically sets off code P0455.
8 Common P0455 Code Symptoms
Here are symptoms to watch out for if you suspect a leak in your vehicle’s EVAP system:
1. Illuminated ‘Check Engine Light’
This indicator almost automatically occurs once the PCM detects an EVAP system leak. It may or may not happen alongside P0455 and other accompanying error codes.
Note that a triggered CEL could also mean a defective diagnostic leak tester.
2. Emissions Test Failure
It’s the 2nd most common symptom and sometimes happens before the P0455 Jeep code displays on the dash.
Having a large EVAP leak is sure to release harmful fumes into the environment. Hence, a failed emissions test would indicate a compromised emissions control system.
3. Decreased Fuel Efficiency
It may be difficult to notice for smaller leaks. But for large EVAP leaks, their bearing on fuel efficiency can no longer be ignored.
So, if you observe a drastic decline in your vehicle’s fuel economy, expect to get the P0455 Jeep code sooner than later. While you’re at it, check that you don’t have a failing PCM.
4. Fuel System Service Light Is On
Since a compromised EVAP system means that one or more fuel system components are defective or damaged, you’d likely get this warning indicator before scanning the P0455 code.
5. Engine Performance Issues
Engine hesitation and misfiring (among others) are usually the result of a malfunctioning or defective EVAP charcoal canister valve or purge solenoid. At other times, a considerable vacuum leak may cause them.
These drivability inconsistencies typically become noticeable when driving at low speeds or during stop-and-go traffic.
6. Stalling/No-Start Issues
Since your car’s EVAP system controls vapor, a large leak is guaranteed to adversely impact how efficiently it starts and runs.
Furthermore, EVAP leaks cause interruption to your vehicle’s internal combustion – which, in turn, leads to performance irregularities such as engine stalling and no-start issues. At best, your car may feel sluggish even without abuse or hard driving.
7. Fuel/Gasoline Smell
This telltale sign is usually associated with an EVAP system leak that has been around for a while. When this happens, you may even notice the smell of burning carpet or fuel in the cabin.
8. Excessive Smoke From the Exhaust Pipe
Because EVAP leaks interrupt a car’s internal combustion, they cause performance problems and excessive exhaust smoke.
This is from not all fuel burning in the combustion chamber. However, this symptom calls for proper diagnosis, as excessive smoke from the exhaust pipe is usually associated with a coolant leak, clogged air filter, or an internal engine oil leak.
P0455 Jeep Code – Possible Causes
Several things could cause an EVAP leak – from an ill-fitted fuel tank cap to a damaged catalytic converter. Similarly, there are also multiple areas in your car’s EVAP system where leakage could occur.
That said, it is best to look into the following at the first sign of a P0455 Jeep code:
- Malfunctioning gas cap or purge vent valve
- Misplaced/loose/damaged gas cap
- Damaged/deformed fuel filler tube or gas cap O-ring
- Obstruction in the fuel filler cap
- Incorrect gas cap used
- Cracked/damaged fuel tank
- Fuel tank or EVAP canister leak
- Leaking/disconnected/punctured EVAP hose
- Leaking/damaged charcoal canister
- Defective canister valve
- Vacuum feed line or control valve leaks
- Sticky/faulty EVAP vent solenoid or purge valve
- Faulty FTP sensor or Leak Detection Pump
- Premature/failing catalytic converter
- Failing or defective PCM
- Poor vehicle upkeep, disregard for periodic inspection, or change of fuel system components and EVAP-related sensors
- Not having a complete vehicle inspection at least once a year
Failing Catalytic Converter
In the case of a failing catalytic converter, you’d know for sure it’s the culprit if you encounter any one of the below symptoms:
- Catalytic converter damage or corrosion
- Compression misfiring from leaky valves
- Internal coolant leaks due to head gasket cracks
- Ignition misfiring from a shorted plug wire
- Oil burning from worn valve guides
- Fuel contamination
While DTC P0455 has a relatively low severity level, it isn’t advisable to continue driving with the code’s problem source still unresolved.
Unlike code P0456, Jeep code P0455 signifies a large EVAP leak with a capacity to emit toxic fumes at a faster rate if left unattended. Not only will your vehicle registration be compromised, but you will also continue to experience unsatisfactory (not to mention unreliable) vehicle performance.
P0455 Jeep Code – Diagnosis & Fix
1. Check TSBs
Check related TSBs (Technical Service Bulletins) for existing issues specific to your vehicle’s EVAP system and its relevant components.
2. Scan for Other Codes
Using a high-spec OBD-II scanner capable of updating live data streams like an Autel Maxisys Elite II Auto Scanner (view on Amazon), scan your vehicle while checking for other error codes apart from P0455.
Don’t forget to read the freeze-frame data and document your findings during this step. Tend to the other fault codes first and clear them in the order they were stored by the PCM to see if doing so lifts the P0455 EVAP code.
Tip: Be on the lookout for codes P0441, P0440, or P0446, as they typically indicate more complicated EVAP system leaks or a solenoid failure.
3. Examine Gas Cap
Examine your vehicle’s gas cap for looseness or damage, and tighten or replace it as needed. Make sure to include gas cap O-rings when you inspect.
If tightening the fuel cap or replacing damaged parts doesn’t reset the code, proceed to the next step.
4. Check for Leaks
Using an EVAP smoke machine/tester, check for visible leaks around the vacuum hoses, charcoal, EVAP canister, and in the fuel tank.
Replace damaged parts as needed should you come across any leak. Otherwise, inspect if the EVAP hoses connected to the engine air box are disconnected or damaged.
Tip: Another way to check for leaks is to ‘wand’ an unlit propane torch over vacuum lines while at idle – doing this will cause fluctuations in engine RPM, which would point you towards the leak source.
5. Look for Blockage
If there is no sign of a leak or visible damage, check for any obstruction or blockage in your car’s purge valve vent (typically found under the hood, near the inbox, or intake manifold). Dirt, debris, and spiderwebs can prevent a total vapor seal in the purge control valve, which the PCM could interpret as an EVAP leak.
6. Test the Purge Volume Control Valve
If your vehicle’s purge valve vent is blockage-free, proceed to check that the purge volume control valve is operating up to spec. You can test this by removing hoses from both sides and blowing through the openings while no power is supplied to the valve.
You should be unable to blow through if the valves are sealing properly. Otherwise, it means the purge control valve has either developed a leak or gotten sticky.
7. Test the Charcoal Canister Vent Valve
Find your car’s charcoal canister vent valve (usually connected to the charcoal canister underneath the vehicle) and do a similar test while ensuring no power is applied to the valve. But this time, air should pass through the openings when you blow through them. If air doesn’t go through, it means there is something wrong with the charcoal canister.
Supplying fused power to one side and grounding the electrical connector on the other is another way to test your charcoal canister vent valve. With this approach, expect results similar to the purge volume control valve test – meaning no air should be able to pass through.
Conversely, sending both 12V+ and ground to it should result in closing and opening air through the vent valve during the process. Any other outcome would signify a faulty charcoal canister vent valve that needs replacement.
Code P0455 Repair Cost
The typical cost of running an engine code diagnostic on a car ranges from $95 to $110. Rates usually depend on how many other fault codes accompany the P0455 Jeep code (not to mention your car’s make and model).
Labor-wise, the fee usually falls between $75 and $200 hourly or a minimum of $100 – barring complications.
The below table provides estimated repair costs associated with clearing DTC P0455:
|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
|$190 – $600
|$200 – $600
|Fuel Filler Tube/Neck/Inlet
|$200 – $850
|Vacuum Feed Line
|$100 – $1,000
|$400 – $1,100
|PCM or ECM
|$800 – $2,000
|$200 – $3,750
These estimates cover relevant parts and labor costs required for the repair (but sans taxes and fees). Should a replacement part be warranted, prices would change depending on whether you lean towards an OEM or aftermarket product.
Ultimately, the location of the leakage and its cause would determine your total repair expenses.
Fixes to Large EVAP Leaks
Although P0455 code symptoms are more apparent than those of small EVAP leaks, their root cause isn’t always necessarily complicated. That said, one of the fixes below should resolve the issue:
- Tighten a loose gas cap (or replace it with the right one if it’s ill-fitted)
- Get a new gas cap or O-ring in case of cracks or damage
- Remove blockage from the fuel filler cap and inlet
- Swap out the leaking/plugged purge vent valve
- Change the EVAP hose or purge control valve
- Resolve breaks/disconnections in EVAP hoses
- Replacing damaged vacuum feed lines
- Cleaning the fuel tank of contaminants causing air leaks
- Replacing a faulty diagnostic leak tester
- Repairing damaged wiring/connectors
Seek Out a Professional Mechanic
Note that this non-exhaustive list does not cover complex leaks. A jeopardized EVAP system that traces back to a leaking fuel tank, defective LDP/FTP sensor, or bad charcoal canister isn’t part of the remedies above.
If the problem source of your P0455 Jeep code turns out to be complicated or sets off other fault codes like P0442, P0440, or P0445, outsource the task right away to a professional mechanic, who should be able to narrow down the issue and resolve it for you permanently.
Conclusion – P0455 Code Symptoms & Fix
Because a vehicle’s PCM only runs an EVAP leak test when fuel levels are between 15% and 85%, spotting P0455 Jeep code symptoms early on, narrowing down their problem source, and promptly resolving them is a crucial set of skills for car owners.
Not only will these skills save you from emptying your pockets on a major overhaul, but they’ll also ensure your four-wheeler always gives off clean emissions. Hopefully, this guide has equipped you with enough working knowledge to accomplish both.
Kris is an avid off-roader and outdoor enthusiast who loves to brave the elements and take on challenging terrain. He also enjoys sharing his passion and knowledge with others so that they, too, can appreciate the ride.