P0455 Code Meaning (Jeep Grand Cherokee) – Causes & Fix

JeepSUVUpdated 2026-04-10

The P0455 OBD-II trouble code is one of the most common codes seen on Jeep Grand Cherokee models and one of the least alarming. It signals that the vehicle's Evaporative Emission Control (EVAP) system has detected a large leak — meaning fuel vapors are escaping the sealed fuel system rather than being routed to the engine for combustion. On the Jeep Grand Cherokee, this code is triggered more often by a loose or faulty gas cap than by any internal component failure. While the check engine light will illuminate, the vehicle remains driveable in virtually all P0455 cases. This guide explains exactly what P0455 means on the Grand Cherokee, the ranked list of causes, and every fix from the simplest to the most involved.

Quick Answer

What it means

The EVAP system has detected a large vapor leak. Fuel vapors are escaping the fuel system. Most commonly caused by a loose or faulty gas cap.

Severity

Low

Can you fix it yourself?

Yes — in most cases a new gas cap or a purge valve replacement resolves P0455.

Call a technician when

If the code returns after replacing the gas cap and a smoke test is needed to locate the leak source.

What Does P0455 Mean?

P0455 stands for 'Evaporative Emission Control System Leak Detected (Large Leak).' The EVAP system in the Jeep Grand Cherokee is a closed network of hoses, valves, a charcoal canister, and a vent solenoid that captures gasoline vapors from the fuel tank and redirects them into the engine to be burned during normal combustion. This prevents raw fuel vapors from venting to the atmosphere, where they contribute to smog.

The EVAP system is monitored by the PCM (Powertrain Control Module) through periodic pressure and flow tests run while the vehicle is in operation. When the PCM detects that vapor pressure is dropping faster than expected — indicating a leak larger than 0.040 inches — it stores P0455 and illuminates the check engine light.

On the Jeep Grand Cherokee (all generations including WJ, WK, WK2, and WL), P0455 has a well-documented set of common causes that are specific to this platform:

Gas cap — The leading cause across all generations. The Jeep Grand Cherokee's gas cap is a common wear item. The rubber seal degrades over time, and even not tightening it completely after refueling will trigger P0455.
EVAP purge solenoid — The purge valve on 3.6L Pentastar and 5.7L HEMI Grand Cherokees is a frequent failure point, particularly on vehicles with 80,000+ miles.
EVAP canister vent valve — Located near the fuel tank, the vent valve can stick open, creating a large continuous leak that the PCM detects immediately.

What Causes This Error?

Loose, damaged, or worn gas cap — most common cause by far
Failed or stuck-open EVAP purge solenoid valve
Cracked or disconnected EVAP hose in the engine bay or under the vehicle
Failed EVAP canister vent solenoid (stuck open)
Cracked charcoal canister — more common on high-mileage Grand Cherokees exposed to road debris
Damaged fuel filler neck or filler tube seal
Fuel tank pressure sensor failure causing a false large-leak reading
Split or deteriorated EVAP vapor line near the fuel tank (common on older WJ and WK models)

How to Fix P0455

1
Check and replace the gas cap first. Remove the gas cap, inspect the rubber seal for cracks, flattening, or debris. Reinstall it and tighten until it clicks three times. Clear the P0455 code with an OBD-II scanner and drive normally for one full drive cycle (a mix of city and highway). If the code does not return, the gas cap was the cause. If the code returns within 1–2 drive cycles, purchase a Mopar OEM replacement gas cap — aftermarket caps frequently do not seal correctly on Jeep Grand Cherokees.
2
Inspect all accessible EVAP hoses in the engine bay. With the hood open, locate the large-diameter hose running from the intake manifold to the purge solenoid. Check for cracks, splits, or disconnected ends. Also inspect the smaller hoses near the firewall. Any cracked hose is a confirmed leak source and should be replaced.
3
Test the EVAP purge solenoid. The purge valve is located on the intake manifold or near the throttle body depending on the engine (3.6L or 5.7L). With the engine cold and off, disconnect the vacuum hose from the purge solenoid and blow through it — you should not be able to push air through it when unpowered (it should be normally closed). If air flows freely, the valve is stuck open and must be replaced. Purge solenoid replacement is a straightforward DIY repair on the Grand Cherokee.
4
Inspect the EVAP canister vent solenoid. This component is located under the vehicle near the fuel tank (rear passenger side on most Grand Cherokee generations). Disconnect the electrical connector and check for corrosion. The vent solenoid should be normally open (air flows freely when unpowered) — if it is stuck closed, it can also trigger EVAP codes though usually smaller ones. Replace if the connector shows heavy corrosion or the valve tests incorrectly.
5
Have a smoke test performed at a shop if the code returns after a new gas cap and visual hose inspection. A smoke machine pressurizes the EVAP system with low-pressure smoke and makes leaks instantly visible. This is the definitive diagnostic for locating leaks that cannot be found visually. Most shops charge $75–150 for a smoke test. Bring the P0455 code history — shops will focus on large-leak sources first.
6
Clear the code after each repair attempt and complete at least two full drive cycles before checking for return. The PCM must run its EVAP monitor test — which requires specific driving conditions including a cold start, a period of highway speed, and engine-off cooling time — before it will confirm the repair. Do not assume a repair failed after only one short drive.

When to Call a Professional

If P0455 returns after a new gas cap and the smoke test locates a leak in the charcoal canister, fuel tank vapor lines, or filler neck area, professional repair is recommended. Fuel tank component access on the Grand Cherokee requires raising the vehicle safely and working around the fuel system. Charcoal canister replacement on WK2 and WL Grand Cherokees requires dropping the spare tire and accessing the undercarriage. Any repair near the fuel tank should be performed by a certified technician with proper equipment.

Can You Still Use the Device?

Yes — P0455 does not affect engine performance, fuel delivery, or vehicle safety. The Grand Cherokee is fully driveable with this code active. The check engine light will remain on, which may cause a failed emissions inspection in states that require OBD-II readiness checks. Address the code before your next emissions test.

Official Resources

Disclaimer: This article is for informational purposes only and does not constitute professional repair advice. CodeExplain is not affiliated with Jeep or any other brand mentioned. Always consult a qualified technician for complex repairs.