Powertrain, generic · Auxiliary emission controls

P0440 EVAP System

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. P0440 is the general code for a fault in this system without further narrowing down – leak, purge flow or component. Today most makers use the specific codes instead (P0441 ff, P0455–P0457, P0496); the GM and Ford tables of 2006–2023 do not contain P0440. It appears in VW code lists and in an FCA bulletin for the Alfa Romeo 2.0, fixed by software, where FCA calls it incorrect flow. What sets it is therefore manufacturer-specific; CARB requires purge flow and leaks to be monitored.

Likely causes

Fuel cap leaking, loose or wrong
Purge valve leaking or sticking
Leaking or cracked EVAP hoses, canister or vent valve
Engine module software

Symptoms

  • Check engine light on
  • Possibly slight fuel smell
  • Readiness or emission inspection not passed
  • No change in driving

Repair estimate

DifficultyMediumDIY possible
Parts and labour€0–400
Time0.2–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

What to check first

  1. Check the fuel cap seal
  2. Smoke-test the EVAP system
  3. Test purge and vent valves

Parts involved

evap systemfuel capevap purge valvecharcoal canister

Related codes

P0441P0442P0455P0456P0457P0443

References: law.cornell.edu, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.