Fault Family System: Powertrain (P-Codes) 3 SAE Codes

EVAP Large Leak

Diagnostic & Technical Explanation

Code P0455 (EVAP System Leak Detected - Large Leak) sets when the EVAP leak-detection monitor detects a leak far larger than the small-leak threshold (roughly equivalent to a 0.040 in. orifice or bigger), including the fuel-tank-side and fresh-air-side variants on natural-vacuum leak detection systems. This points to a substantially open path to atmosphere: a fuel cap left off or badly damaged, a disconnected or split EVAP hose, or a canister/valve that has failed open.

These 3 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 3 times.

Codes in this family (3)

Code	Definition	Repair coverage
P0455	EVAP System Leak Detected - Large Leak	4 ranked fixes
P04EC	EVAP System Large Leak Detected - Fuel Tank Side	4 ranked fixes
P04ED	EVAP System Large Leak Detected - Fresh Air Side	4 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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