Fuel filler cap loose, missing, worn or with a perished seal; Faulty or sticking EVAP purge valve or vent valve (leaking when it should be closed); Cracked, split or loose EVAP hoses, hardened O-rings or poorly seated quick-release connectors; Leak from the carbon canister, including seam splits or damage from road debris or corrosion; Leaking fuel pump or sender unit flange seal on the tank; Faulty fuel tank pressure sensor or leak detection pump (where fitted, depends on model and year); Damaged or distorted filler neck, or a corroded or damaged fuel tank.

P0442

Defective or damaged fuel cap, Distorted or damaged Fuel Tank Filler Neck, Small tear or puncture in the Evaporative system hose(s) and or Carbon Canister, Defective Fuel Tank Sending Unit gasket or seal, Small split in a seam of the Carbon Canister, Defective Evaporative Vent Valve and or Evaporative Purge Valve, Defective or damaged Fuel Tank, Defective Fuel Tank Pressure Sensor, Defective Leak Detection Pump, Slightly loose and or worn clamps or hardened O-rings anywhere in the EVAP system.

Audi
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
42: FaultThe specific fault in that area

What it means

P0442 means the engine control unit has run its evaporative emission (EVAP) system leak test and found a small leak. The EVAP system traps fuel vapour from the tank in the carbon canister and feeds it to the engine through the purge valve. On Audi models the test usually pressurises or applies vacuum to the system and watches for pressure decay, so the code sets when the system fails to hold pressure as expected.

Symptoms

Engine management light on
Smell of fuel vapour around the car or fuel filler, especially after parking
Fuel cap warning message or a cap that clicks poorly or feels loose
Slightly worse fuel economy in some cases
Often no change in driving behaviour at all
Hard starting or rough idle after refuelling if the purge or vent valve is sticking

Possible causes

Fuel filler cap loose, missing, worn or with a perished seallikely
Faulty or sticking EVAP purge valve or vent valve (leaking when it should be closed)likely
Cracked, split or loose EVAP hoses, hardened O-rings or poorly seated quick-release connectorslikely
Leak from the carbon canister, including seam splits or damage from road debris or corrosionpossible
Leaking fuel pump or sender unit flange seal on the tankpossible
Faulty fuel tank pressure sensor or leak detection pump (where fitted, depends on model and year)possible
Damaged or distorted filler neck, or a corroded or damaged fuel tankrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting any related EVAP codes such as purge or vent valve faults, and check whether the code returned after the cap was last touched.
Inspect the fuel cap for a damaged or perished seal, a cracked body or a missing tether, and make sure it clicks tight when refitted.
Visually inspect the filler neck and all accessible EVAP hoses, connectors and clamps for cracks, disconnection, chafing or hardened seals, including around the canister and under the rear of the car.
Using diagnostic equipment, command the purge valve and vent valve and listen for operation, then check that each holds vacuum when closed.
View live data for the tank pressure sensor and confirm plausible readings with the system open to atmosphere; check the sensor wiring and connector.
Smoke test the EVAP system at low pressure to find the leak source, following the manufacturer procedure for the specific model.
Where a leak detection pump is fitted, check its operation and wiring, as the procedure varies by model and engine.
Inspect the fuel pump flange seal and tank for leaks or corrosion once the easier items are ruled out.

How to fix

Replace the fuel cap with a correct one if the seal or body is worn or damaged.
Replace the faulty purge valve or vent valve and clear any related fault.
Replace cracked or split hoses, damaged connectors and hardened O-rings, and reseat all connections fully.
Replace a leaking carbon canister or the damaged filler neck.
Renew the sender unit or fuel pump flange seal if it is leaking.
Replace a faulty tank pressure sensor or leak detection pump, then clear codes and confirm the monitor runs and passes.

Can I keep driving?

Low severity

The car is generally safe to drive and the leak is small, so you can keep driving and book a repair. If you can smell strong fuel or see liquid fuel leaking, have it checked promptly as that is a fire risk.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.