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GTECH Calibration
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P0440

Missing fuel cap, Defective or damaged fuel cap, Distorted or damaged Fuel Tank Filler Neck, Torn or punctured Evaporative system hose(s), Defective Fuel Tank Sending Unit gasket or seal, Split or damaged Carbon Canister, Defective Evaporative Vent Valve and or Evaporative Purge Valve, Defective or damaged fuel tank.

  • 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
40
FaultThe specific fault in that area

What it means

P0440 on an Audi means the engine control unit has detected a fault in the evaporative emission (EVAP) system, which captures fuel vapour from the tank and feeds it to the engine. During a self-test the system failed to hold the expected vacuum or pressure, or the valves did not respond as expected, which points to a leak or a faulty valve. The code does not say where the fault is, so it needs to be traced.

Symptoms

  • Engine management light on
  • Fuel smell around the car or near the filler
  • Difficulty refuelling, such as the pump clicking off repeatedly
  • Hissing from the fuel filler when the cap is removed
  • Usually no change in driveability
  • Possible rough idle or hesitation if the purge valve is stuck open

Possible causes

  • Fuel filler cap missing, loose, worn or with a damaged seallikely
  • Faulty or stuck EVAP purge valve (tank vent or canister purge solenoid)likely
  • Cracked, split or disconnected EVAP hoses or quick-release connectorslikely
  • Faulty EVAP vent valve or blocked vent or filter on the carbon canisterpossible
  • Damaged or cracked carbon canisterpossible
  • Distorted or corroded fuel filler neck, or a leaking fuel pump or sender flange sealpossible
  • Damaged fuel tank, or a fault in the tank pressure sensor or its wiringrare

How to diagnose

  1. Read the stored codes and freeze frame data, and note any other EVAP, fuel trim or tank pressure codes and the conditions when the fault set.
  2. Check the fuel cap is present, fits correctly, clicks tight and has an undamaged seal, and inspect the filler neck for damage or corrosion.
  3. Visually inspect all accessible EVAP hoses, connectors and the canister for cracks, splits, disconnections and road damage.
  4. Inspect the wiring and connectors to the purge valve, vent valve and any tank pressure sensor for damage, corrosion or water ingress.
  5. Use a diagnostic tool to activate the purge and vent valves and listen for operation, and check live data for tank pressure.
  6. Test the purge valve and vent valve for sticking and for sealing when closed, following the procedure for the specific model and engine.
  7. Smoke test the EVAP system to locate leaks, including the fuel pump or sender flange seal, the canister and the tank.
  8. Clear the code after the repair and run a drive cycle to confirm the self-test passes.

How to fix

  • Replace the fuel cap with a correct one if it is missing, loose or damaged.
  • Replace a faulty purge valve or vent valve.
  • Repair or replace leaking or disconnected EVAP hoses and connectors.
  • Replace a cracked canister or a blocked vent filter.
  • Replace the sender or pump flange seal or a damaged filler neck.
  • Repair any wiring fault or replace a faulty tank pressure sensor, then confirm the monitor completes.

Can I keep driving?

Low severity

The car is normally safe to drive and it can be booked in at a convenient time. Have a strong fuel smell or visible fuel leak checked promptly, as that is a safety concern.

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

This code for other makes

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