Powertrain, generic · Auxiliary emission controls

P04EE EVAP System Very Small Leak Detected - Fuel Tank Side

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Hybrids with a sealed fuel tank have a valve separating the tank from the charcoal canister and its vent side. CARB allows such sections to be leak-checked separately with their own codes; a Ford patent checks the tank side via tank pressure with the valve closed and the canister side with a leak check module. Conventional systems report the same leak as P0442, P0455 or P0456. P04EE reports a very small leak (0.020 in) in the tank section, usually checked with the engine off. Stellantis documents it on the Jeep Wrangler 4xe – cap, tether or filler tube, with a scan-tool leak test before replacing parts – and Ford on the C-Max, Fusion and MKZ hybrids and Energi of 2013–17, together with P0456 and P0457, fixed by a tighter purge valve and software.

Likely causes

Fuel cap seal deformed or dirty, tether trapped
Purge valve not sealing (Ford hybrids) – plus software
Leaking quick connector or vent line at the tank
Hairline crack in tank lines or flange seal

Symptoms

  • Check engine light on
  • Check fuel cap message
  • No change in driving

Repair estimate

DifficultyEasyDIY possible
Parts and labour€0–350
Time0.1–1.5 h

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

Parts involved

fuel tankfuel capevap purge valvefuel tank pressure sensor

Related codes

P04EAP04ECP04EFP0456P2450

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