Fuel filler cap loose, missing, worn or fitted with a damaged seal; Cracked, perished or poorly seated filler neck seal or filler neck pipe connection; Leaking EVAP pipe, hose or quick-release connector on the tank side; Faulty fuel tank pressure sensor giving an inaccurate reading; Leaking vent valve, shut-off valve or tank isolation valve not sealing fully; Damaged or leaking fuel tank, tank seal or fuel pump or sender flange seal; Charcoal canister cracked or its connections leaking, depending on layout.

P04EE

EVAP System Very Small Leak Detected - Fuel Tank Side.

Generic
Powertrain
Generic code
Low severity

How this code is built

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

What it means

P04EE means the evaporative emission (EVAP) control system has detected a very small leak on the fuel tank side of the system, between the tank and the purge or vent valve area. The control unit runs a leak test, usually by sealing the system and applying vacuum or pressure, then watches for the pressure change to decay faster than allowed. The exact test method and the precise boundary of the 'tank side' vary by manufacturer and model.

Symptoms

Engine management light on
No noticeable change in driving in most cases
Occasional faint fuel smell near the rear of the car or around the filler
Fuel filler cap warning message on some models
Failed emissions or inspection readiness test due to incomplete monitors

Possible causes

Fuel filler cap loose, missing, worn or fitted with a damaged seallikely
Cracked, perished or poorly seated filler neck seal or filler neck pipe connectionlikely
Leaking EVAP pipe, hose or quick-release connector on the tank sidepossible
Faulty fuel tank pressure sensor giving an inaccurate readingpossible
Leaking vent valve, shut-off valve or tank isolation valve not sealing fullypossible
Damaged or leaking fuel tank, tank seal or fuel pump or sender flange sealrare
Charcoal canister cracked or its connections leaking, depending on layoutrare

How to diagnose

Read the stored and pending codes and review freeze frame data, noting fuel level, temperature and the conditions when the fault set
Check for other EVAP, fuel level or tank pressure codes that might point to a sensor or valve fault rather than a leak
Inspect the fuel filler cap for correct fitting, a damaged seal or the wrong type, and check the filler neck sealing surface
Visually inspect accessible EVAP pipes, hoses, connectors and wiring on the tank side for damage, corrosion or disconnection
Check live data for the fuel tank pressure sensor with the system open to atmosphere, and compare it with the expected reading
Command the vent and purge valves with a scan tool where supported, and check they operate and seal, following the model's procedure
Carry out a smoke test of the EVAP system at the manufacturer's specified low pressure to locate the leak
Inspect the tank, fuel pump flange seal and filler neck for leaks once the smoke test points to that area

How to fix

Fit a correct, undamaged fuel filler cap or replace the cap seal
Replace the damaged filler neck seal, pipe or connection
Repair or replace leaking EVAP pipes, hoses or connectors
Replace a faulty tank pressure sensor if its readings are wrong
Replace a vent, shut-off or isolation valve that fails to seal
Replace a leaking fuel pump flange seal, canister or tank as confirmed by testing

Can I keep driving?

Low severity

The car can normally be driven as usual, as a very small EVAP leak does not affect safety or engine running. Book it in soon, especially if you can smell fuel, as the fault will keep the warning light on and may cause an inspection failure.

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