P0442 Evap Emission Control System Small Leak Detected

Code: P0442
Applies To: Most makes, generic code
Leak Size: .040 inch or bigger
Loose Cap Can Set It: Yes
Diagnosis: $61 to $90 at RepairPal

The computer found a small leak somewhere in the fuel vapor system.
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 small leak detected, as printed by Volkswagen Group of America
Evaporative Emission (EVAP) System Small Leak Detected, as printed by General Motors
EVAP system leak detected (small leak), as printed by Mazda North American Operations

Causes Named In Carmaker Bulletins

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 and Avalanche) (source)
Air leaks in the EVAP system or in the leak detection pump itself (2013 to 2014 Audi Q7) (source)
A loose fuel filler cap on some Mazda3, Mazdaspeed3 and Mazda5 models, fixed with an improved cap (source)

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

Mazda points to an improved cap for loose cap P0442, P0455 and P0456 (TSB 01 020/10).

How Small Is The Leak

Ford sets P0442 for a 0.040 inch leak on its engine running test

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 what to do after a failed 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.

P0456Evap System Very Small Leak P0440Evap Emission Control System Malfunction P1450Excessive Vacuum