Unable to Bleed Up Fuel Tank Vacuum

What it means

This is a Ford, Lincoln and Mercury code; the same number can mean something different on other makes. The engine computer saw excess vacuum in the fuel tank that did not bleed off as expected during the EVAP test. The cause is usually a blocked canister vent path or a vent valve stuck closed.

Models covered: Ford (and Lincoln/Mercury) models, mainly around 1996–2006.

Related codes: P0446P0449P0441P0452P0453

Symptoms4

• Check engine light on.
• Hard refueling, with the nozzle clicking off repeatedly.
• Strong rush of air when the fuel cap is opened.
• In severe cases the tank can deform or the fuel gauge can be affected.

Possible causes6

• Canister vent valve stuck closed.
• Vent hose or its air filter blocked by dust, mud or insects.
• Purge valve stuck open, pulling constant vacuum.
• Kinked or blocked vapor lines.
• Faulty fuel tank pressure sensor giving a wrong reading.
• Saturated or damaged canister.

How to diagnose5

1. Open the fuel cap after a drive and note any strong rush of air.
2. Command the vent valve with a scan tool and confirm it opens and passes air.
3. Check the vent hose and its filter for blockage.
4. Confirm the purge valve fully closes when commanded off.
5. Watch the tank pressure sensor reading as the cap is opened and closed.

How to fix5

1. Clear the blocked vent hose and filter.
2. Replace the canister vent valve.
3. Replace the purge valve if it is stuck open.
4. Repair kinked lines or replace a damaged canister.
5. Clear the code and confirm easy refueling and a passing system test.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

Clearing the vent path may be enough at low cost; the cost rises when valves or the canister must be replaced.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions