P0455 on a Ram 1500
Evaporative Emission System Leak Detected (Large Leak)
5.7L HEMI V8 and 3.6L Pentastar V6
What P0455 usually means on a 1500
P0455 is a large evaporative-emissions leak on the Ram 1500, meaning the sealed fuel-vapor system is losing containment in a big way. The most common trigger is a loose, worn, or cross-threaded gas cap, followed by the EVAP purge and vent valves. On a truck, cracked or chafed vapor lines under the bed and near the tank are also worth inspecting. It will not affect how the truck drives, but it keeps the check-engine light on and fails emissions.
Most likely causes on this model
- Loose or worn gas cap
Tighten to several clicks and inspect the seal; a bad cap is the number-one P0455 cause.
- Stuck-open purge valve
A purge solenoid that will not seal leaks the system and sets a large-leak code.
- Vent valve fault
A vent valve stuck open keeps the system from holding vacuum during the self-test.
- Cracked or chafed vapor line
On a pickup, vapor lines routed near the tank and frame can chafe or crack and leak.
What it costs on a 1500
If a gas cap fixes it, the cost is trivial. Valves and hoses are inexpensive parts, so most of any bill is diagnostic smoke-testing time, usually a modest few hundred dollars at most. This is a low-stakes repair with no drivability risk, so there is no rush beyond an emissions deadline.
Year, engine and mileage change the answer. Get a diagnosis for your 1500 — it weighs these causes against your exact configuration and real complaint data.
Diagnose my 1500 free →Other codes we cover on the Ram 1500
Related symptoms
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.