P0455 on a Jeep Grand Cherokee
P0455 means evaporative Emission System Leak Detected (Large Leak). On the Grand Cherokee, a few causes come up far more than others.
What P0455 usually means on a Grand Cherokee
P0455 is a large evaporative-emissions leak on the Grand Cherokee, meaning the sealed fuel-vapor system is losing pressure or vacuum in a big way. The number-one cause across these trucks is a loose, cross-threaded, or worn gas cap, followed by the EVAP purge and vent valves. WK2 owners also see cracked vapor lines and, less often, a failed leak-detection component. It will not hurt the truck, but it keeps the check-engine light on and fails emissions.
Most common causes on the Grand Cherokee
- Loose or worn gas cap
Tighten it to several clicks and inspect the seal; a bad cap is the single most common P0455 trigger.
- Stuck-open purge valve
A purge solenoid that will not seal lets the system leak and sets a large-leak code.
- Vent valve fault
A vent valve stuck open prevents the system from holding vacuum during the leak test.
- Cracked or disconnected EVAP hose
Age-hardened vapor lines split and are easy to miss without a smoke test.
What P0455 costs to fix on a Grand Cherokee
If a gas cap fixes it, you are out about the price of a cap and a drive cycle. Valves and hoses are inexpensive parts but can take diagnostic time to pinpoint, so most of the bill is a smoke test and labor, usually a modest few hundred dollars at most. This is a low-stakes repair you can take your time on.
Year, engine and mileage change the answer. Start a case and Redline weighs these causes against what your car shows, then names the check that would settle it.
Grand Cherokee owners also ask
Can a gas cap really set P0455 on my Grand Cherokee?
It can — a loose or worn cap is the most common cause of a large EVAP leak. Tighten it firmly, let several drive cycles pass, and if the light does not clear, move on to the purge and vent valves.
Will P0455 make my Grand Cherokee run poorly?
No. An EVAP leak affects emissions and vapor containment, not how the engine runs, so drivability stays normal. It does keep the check-engine light on and will fail an emissions test until fixed.
Other codes on the Jeep Grand Cherokee
Related symptoms
Jeep Grand Cherokee problems & recalls by year
Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0455 behavior is covered on the main P0455 page. Confirm with a scan tool before buying parts.
P0455 on your Grand Cherokee?
Every problem becomes a Case. Tell Redline what your Grand Cherokee is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.