P0455 on a BMW: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

Safe to drive — this is an emissions leak, not an engine problem, but fix it before your next emissions test.

What P0455 means on a BMW

On a BMW, P0455 means the engine computer has detected a large leak in the evaporative emission (EVAP) system, so fuel vapors are escaping. On BMWs the gas cap is still a common culprit, but the leak diagnosis module pump and the fuel tank vent valve are also known trouble spots.

Is P0455 common on BMWs?

P0455 shows up on BMWs like the 3 Series, 5 Series, X3, and X5, often on older models. Beyond the gas cap, BMW's EVAP system has a leak diagnosis pump that can fail, and a smoke test will separate a simple cap issue from a real leak.

Commonly reported on: 3 Series, 5 Series, X3, X5.

Symptoms

Check engine light is on
Possible fuel smell
No driving symptoms
Emissions test failure

Common causes

most common: Loose or damaged gas cap
common: Faulty leak diagnosis module pump
common: Faulty fuel tank vent valve
less common: Cracked EVAP hose or vent line

How to fix it

Fix	DIY?	Typical cost
Tighten or replace the gas cap	Yes	$10–30
Have a smoke test performed to find the exact leak	Mechanic	$80–180
Replace the leak diagnosis module pump	Mechanic	$150–350
Replace a faulty vent valve	Yes	$60–160