EVAP System Leak Detected Gross Leak/No Flow
Table of contents
P0456 MERCURY Possible Causes
- Missing or loose fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- Evaporative Emission (EVAP) canister or fuel tank leaks
- Evaporative Emission (EVAP) system hose leaking
- Fuel tank leaking
How do I fix code P0456 MERCURY?
Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector’s pins.
Tech Notes
- There is a factory service bulletin for the following Mercury vehicles:
- 1997-1999 Mercury Tracer
- 1997-2000 Mercury Mystique
- 1997-2003 Mercury Grand Marquis
- 1997-2003 Mercury Sable
- 1999-2002 Mercury Cougar
- 1997-2003 Mercury Mountaineer
- Mercury Factory Service Bulletin OBDII Code P0456
Cost of diagnosing the P0456 MERCURY code
The cost of diagnosing the P0456 MERCURY code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle’s make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
Possible Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Possible a noticeable fuel odor caused by the release of fuel vapors
P0456 MERCURY Description
This diagnosis detects leaks in the Evaporative Emission System (EVAP) purge line using an engine intake manifold vacuum. If pressure does not increase, the Engine Control Module (ECM) will check for leaks in the line between the fuel tank and EVAP canister purge volume control solenoid valve under the following vacuum test condition.
The vacuum cut valve bypass valve is opened to clear the line between the fuel tank and the EVAP canister purge volume control solenoid valve. The EVAP canister vent control valve will then be closed to shut the EVAP purge line off. The EVAP canister purge volume control solenoid valve is opened to depressurize the EVAP purge line using intake manifold vacuum. After this depressurization is implemented, the EVAP canister purge volume control solenoid valve will be closed.
The Diagnostic Trouble Code (DTC) will set when the EVAP control system has a very large leak such as the fuel filler cap fell off, the EVAP control system does not operate properly.