P0455 Evap Emission Control System Gross Leak Detected

Code: P0455
Applies To: Most makes, generic code
Loose Cap Can Set It: Yes
Typical Fix: $138 to $150 at RepairPal

The computer found a big leak, or the system could not hold the test vacuum at all.
Check the gas cap first. A shop confirms it with the carmaker's EVAP test and a smoke machine before replacing parts.
Usually yes for now, but get it fixed soon and check for open recalls.

What The Carmakers Call It

EVAP emission control system gross leak detected, as printed by Volkswagen Group of America
Evaporative Emission (EVAP) System Large Leak Detected, as printed by General Motors
EVAP system leak detected (gross leak), as printed by Mazda North American Operations
Evaporative Emission [EVAP] System Very Large Leak Detected, as printed by American Honda Motor Co. (Acura)

Where sources differ. Name differs by maker. VW says gross leak, GM and Mazda say large leak, and a 2022 Acura bulletin says very large leak.

Causes Named In Carmaker Bulletins

Ford lists, a fuel cap not installed right, a stuck open capless fuel fill valve, a large hole, an overfilled tank, disconnected or kinked vapor lines, a vent valve stuck open, a purge valve stuck closed, or a blocked line between the purge valve and the tank pressure sensor (source)
A fuel cap gasket with too much friction so the cap does not seal (several 2011 to 2013 Acura models) (source)
A fuel filler main flap stuck open (2021 to 2022 TLX) (source)
A filler neck leak at the mis fuel inhibitor and main flap (2016 Pilot, 2017 Ridgeline) (source)
A split purge valve hose (some 2015 Grand Cherokee and Durango) (source)
A purge valve stuck by oil from the cam cover gasket (2014 to 2018 Impala 3.6L) (source)
Water, dirt or corrosion at the canister vent valve (2007 to 2010 GM full size SUVs) (source)

No source ranks these by how often they happen, so they are listed as the bulletins give them.

Ford names a fuel cap that was not installed right as a P0455 cause. On Fords without the P0457 test, a loose cap sets only P0455.

Ford says 2009 and later models need 2 or 3 gross leak failures in a row before P0455 sets.

How Small Is The Leak

No orifice size is set for P0455 in our sources. On Ford's test it sets when the system cannot pull 8 inches of water vacuum.

What The Fix Costs

The usual part for this code is the gas cap. Published estimates put it at $138 to $150 at RepairPal. The full table with every source and date is on the cost page. A diagnosis first keeps you from paying for a part you did not need, which is why we price readiness monitors and smog check before the fix.

Getting The Light To Go Off

After the repair the light goes off once the EVAP test runs and passes on three drive cycles in a row, and the code is erased after 40 warm up cycles, per CARB. The test only runs under set conditions such as a fuel level between about 15 and 85 percent, so it can take days.

P0457Evap Emission System Leak Detected (fuel Cap Loose/off)P1456Evap Control System Leakage [fuel Tank System]

By Anthony Limpert, co-founder of Supercanic in San Jacinto, California, a shop with ASE certified mechanics. Updated November 12, 2026.

Author Source EEAT Authors · Anthony's Author Page

Sources For This Page

Technical Bulletin 2034072, Canister Purge Valve N80 Diagnosis (July 18, 2013), Volkswagen Group of America, read 2026-11-12
Service Bulletin 17-NA-409, P0442, P0496, P0455 on Impala LFX (February 2018), General Motors, read 2026-11-12
TSB 01-002/18, Determining Evaporative System Leak Location for P0441, P0442, P0455, P0456 (January 30, 2018), Mazda North American Operations, read 2026-11-12
Service Bulletin 21-007 Version 2, MIL Is ON with DTC P0455, TLX (September 2, 2022), American Honda Motor Co. (Acura), read 2026-11-12
2009 MY OBD System Operation Summary for Hybrid Electric Vehicles (revised May 22, 2008), Ford Motor Company, read 2026-11-12
Service Bulletin 14-006, MIL Comes On With DTC P0455 and/or P0456 (February 18, 2014), American Honda Motor Co. (Acura), read 2026-11-12
Tech Line ATS 170206, EVAP leak from the filler neck (February 2017), American Honda Motor Co., read 2026-11-12
Service Bulletin 25-002-15 REV. B, P0455/P0456, 2015 Grand Cherokee and Durango (October 21, 2015), FCA US LLC, read 2026-11-12
Service Bulletin 09-06-04-028D, P0442, P0446, P0455, P0449, hard to fill (April 2014), General Motors, read 2026-11-12
13 CCR 1968.2, Malfunction and Diagnostic System Requirements, OBD II, California Air Resources Board (via Cornell LII), read 2026-11-12
Gas Cap Replacement Cost Estimate, RepairPal, read 2026-11-12