P0456 Evap System Very Small Leak

Code: P0456
Applies To: Most makes, generic code
Leak Size: .020 inch or bigger
Loose Cap Can Set It: Yes
Diagnosis: $61 to $90 at RepairPal

The computer found a very small leak, about the size of a 0.020 inch hole.
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 system very small leak, as printed by US EPA, Code of Federal Regulations (via Cornell LII)
EVAP System Leak Detected (Very Small Leak), as printed by Volkswagen Group of America
EVAP system leak detected (very small leak), as printed by Mazda North American Operations
EVAP emission control system small leak detected, as printed by Volkswagen Group of America

Where sources differ. A 2013 VW bulletin calls P0456 a small leak, the same words it uses for P0442. The federal rule, a 2019 VW bulletin, Mazda and Honda call it a very small leak. FCA's 2015 bulletin also calls P0456 EVAP System Small Leak.

Causes Named In Carmaker Bulletins

No natural vacuum seen after shut off on cars with natural vacuum leak detection (2012 to 2014 Audi A4, A5, A6, A7) (source)
Salt deposits inside the NVLD sensor (2016 to 2019 Sonata Hybrid) (source)
A fuel cap gasket with too much friction so the cap does not seal (several 2011 to 2013 Acura models) (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)
Air leaks in the EVAP system or the leak detection pump (2013 to 2014 Audi Q7) (source)

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

Acura bulletin 14 006 ties P0455 and P0456 to a cap that does not seal.

How Small Is The Leak

Federal rule names P0456 as a generic very small leak code for the 0.020 inch test. Ford's engine off test also sets P0456 for 0.020 inch.

What The Fix Costs

The usual part for this code is the smoke test and diagnosis. Published estimates put it at $61 to $90 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 check engine light 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.

P0442Evap Emission Control System Small Leak Detected P0440Evap Emission Control System Malfunction P1450Excessive Vacuum

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

40 CFR 86.1806 17, Onboard diagnostics, US EPA, Code of Federal Regulations (via Cornell LII), read 2026-11-12
Technical Service Bulletin 2054615/1, Update Programming, 2018 Tiguan (July 1, 2019), Volkswagen Group of America, 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
Technical Bulletin 2034072, Canister Purge Valve N80 Diagnosis (July 18, 2013), Volkswagen Group of America, 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
Technical Service Bulletin 2035073/1, P0456 NVLD very small leak (October 16, 2013), Audi of America, read 2026-11-12
TSB 20-FL-003H, DTC P0456 EVAP very small leak, Sonata Hybrid (May 2020), Hyundai Motor America, 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
Technical Service Bulletin 2035519/1, P0456 or P0442, Q7 (October 23, 2013), Audi of America, 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
Emission System Diagnosis and Testing Cost Estimate, RepairPal, read 2026-11-12