P04EA: EVAP System Small Leak Detected

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. P04EA reports a small leak (0.040 in) in the tank section – tank, filler neck, cap and lines up to the tank valve. No manufacturer document available to us names this code; the description follows CARB and the Ford patent.

Low severity. Can I keep driving?Yes, you can normally keep driving. If there is a strong smell of gasoline, find the leak before continuing and do not smoke nearby.

Symptoms

Check engine light on
Possibly check fuel cap message or slight fuel smell
No change in driving

Most likely causes

Fuel cap or seal leaking or not closed properly (tether trapped)
Filler neck or tank vent line leaking
Sender or pump flange seal leaking
Tank valve or tank pressure sensor faulty

What to check, in order

Start with the simplest. You can tick off each step.

Start with the fuel cap: tighten it fully and check its seal
Inspect the hoses and connections around the tank and the charcoal canister
Use the scanner to test the purge and vent solenoid valves
Run a smoke test to find small leaks

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P04EA means

P: Powertrain: engine and transmission
0: Generic code: same on every make
4: Emissions
EA: Specific fault in that system

Frequently asked questions

Can I keep driving with code P04EA?

Yes, you can normally keep driving. If there is a strong smell of gasoline, find the leak before continuing and do not smoke nearby.

What causes code P04EA?

The most common causes are: fuel cap or seal leaking or not closed properly (tether trapped); filler neck or tank vent line leaking; sender or pump flange seal leaking.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.

P04EA: EVAP System Small Leak Detected - Fuel Tank Side