- Vehicles
- Cars
P0442
P0442 (generic OBD-II): small leak in the EVAP vapour system
Risk level
Low
Usually safe to check without specialist tools.
Urgency
Low
Quick answer
The system that captures fuel tank vapour did not hold vacuum during the small leak test. First check the fuel cap is tightly closed and its seal is clean. If you smell petrol, do not smoke or make sparks nearby.
Safety first
Stop and check this first
- If you smell petrol in or around the car, do not smoke, do not light anything and do not drive; call roadside assistance.
Safe checks you can perform
- Fuel cap
- Other EVAP codes and monitor status
- Persistent petrol smell
Leave these tasks to a qualified professional
- Do not attempt this professional task: EVAP smoke test
- Do not attempt this professional task: Valve test and completed EVAP monitor
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
EVAP smoke test
What they doThe technician feeds smoke into the sealed EVAP system and looks for where it escapes: cap, lines, canister or valves.
They must show youa photo or video of the point where the smoke escapes.
In writingthe part replaced and its number, or that the smoke showed no leak.
Valve test and completed EVAP monitor
What they doThe technician commands the purge and vent valves with the scan tool, checks they seal and, after the repair, lets the EVAP monitor complete again.
They must show youeach valve's response and the EVAP monitor as complete.
In writingwhat was repaired and the date the monitor completed with no code.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Fuel cap
- Who:
- you, with the engine off.
- How:
- remove the cap, check the rubber seal is not cut or dirty and refit it until it clicks or feels firm.
- Result that matters:
- whether the cap was loose or its seal damaged.
- If it was loose or damaged:
- fix it and drive normally for a few days; Nissan says the light goes off after a few trips if there is no other fault.
- If it was fine:
- the cap does not explain the code; move on to reading codes.
- Evidence to keep:
- a photo of the cap and its seal, and the date you checked it.
Do not smoke or use flames when opening the tank.
Evidence: Nissan USA malfunction indicator light guide
Other EVAP codes and monitor status
- Who:
- you, with a generic OBD-II reader.
- How:
- read the codes and note whether P0442 comes with P0455, P0456, P0457 or purge or vent valve codes.
- Result that matters:
- whether there is an electrical valve fault or only a leak.
- If there are valve circuit codes:
- the workshop must fix that circuit first, because the leak test depends on those valves.
- If only P0442:
- treat it as a physical leak; the workshop needs a smoke test.
- Evidence to keep:
- a photo of the codes and the EVAP monitor status.
Use the reader with the car parked. Do not clear: Ford's EVAP test can take days to run again.
Evidence: Ford 2020-2023 gasoline OBD system operation
Persistent petrol smell
- Who:
- you, outdoors with the engine off.
- How:
- check for a petrol smell around the tank, the canister or inside the cabin.
- Result that matters:
- whether the smell is persistent.
- If there is a strong smell:
- do not start the car or smoke; there may be a liquid leak as well as vapour; call for assistance.
- If there is no smell:
- this fits a small vapour leak; book a visit without urgency.
- Evidence to keep:
- where and when you noticed the smell.
Never look for a fuel leak with a flame.
Evidence: Ford 2020-2023 gasoline OBD system operation
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Vehicles
- Brand
- OBD-II genérico
- Product type
- Cars
Known code variants
- P0442
- P0442 EVAP small leak
- P0442 fuga pequeña EVAP
- P0442 OBD2
What it means
P0442 is the generic code for a small leak in the EVAP vapour control system (tank, canister, valves and lines). California's OBD II regulation requires detecting leaks equal to a 0.040 inch orifice. In Ford's summary the test pulls vacuum with the engine running, closes the vent valve and measures how much vacuum is lost. The code does not say where the leak is: it can be the cap, a line, a seal or a valve.
Warnings and stop conditions
- Higheditorial warning
If you smell petrol in or around the car, do not smoke, do not light anything and do not drive; call roadside assistance.
Evidence: Ford 2020-2023 gasoline OBD system operation
Symptoms and causes
Probable causes · in order
- Fuel cap or its sealPossible
A loose cap or damaged seal lets air in. Nissan says to check it when the light is steady. It shows because the code does not return once fixed.
Evidence: Nissan USA malfunction indicator light guide · Ford 2020-2023 gasoline OBD system operation
- EVAP line or hosePossible
A cracked line stops the system sealing. FCA published a case of a split purge hose with EVAP codes. It is located with a smoke test.
Evidence: FCA TSB 25-002-15 Rev A Jeep Grand Cherokee P0455
- Purge or vent valvePossible
Ford requires the purge and canister vent valves to work for the test. If they do not close properly, the system loses vacuum.
Evidence: Ford 2020-2023 gasoline OBD system operation
Virtual technician
Does P0442 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Nissan USA malfunction indicator light guide
Nissan USA · official_doc
- 2
FCA TSB 25-002-15 Rev A Jeep Grand Cherokee P0455
FCA US LLC · 2015 · service_bulletin
- 3
Ford 2020-2023 gasoline OBD system operation
Ford Motor Company · 2023 · manual
- 4
California Air Resources Board · 2006 · official_doc
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