Evap control system gross leak detected.what is that?

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
- EVAP canister or fuel tank leaks
- EVAP system hose leaking
- Fuel tank leaking
What does this mean? Tech notes
The P0455 it's a very common code, because the code is set if the gas cap is loose or missing. Start by tighten the gas cap and clearing the code. In most cases the code can be clear by disconnecting the car battery for about 30 minutes.
What does this mean? When is the code detected?
Evaporative Emission System (EVAP) control system has a very large leak such as fuel filler cap fell off, EVAP control system does not operate properly.
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Possible a noticeable fuel odor caused by the release of fuel vapors
P0455 Mitsubishi Description
This diagnosis detects leaks in the Evaporative Emission System (EVAP) purge line using 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.

Read more: http://engine-codes.com/p0455_mitsubishi.html#ixzz3NlVyARyX

jeep uses whats called a leak detection pump that is the most common failure in the system that i have seen in the last five yeas

P0455 CHEVROLET - Evaporative Emission Control System Leak Detected Gross Leak3http://engine-codes.com/p0455_chevrolet.htmlForum CodePossible 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
- EVAP canister or fuel tank leaks
- EVAP system hose leaking
- Fuel tank leaking

Millions of cars have that issue

The Evap System, will most easily be diagnosed &
your Gross Leak resolved,if you have a repair shop
with an EVAP Smoke Machine put on that system

The Gas Cap would be a PO442 (small leak) The way you
remember is, from the Hurst Olds 442, from the 1960's

The smoke test will blow some out the place of the leak,
like a rotted hose or broken evap valve.


Slow Acceleration---you work on after all check light issues
are resolved such as the evap leak.

P0455 NISSAN - EVAPorative Emissions Control System Gross Leak Detected. Possible causes - Missing or loose fuel cap (most common)
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- EVAP canister or fuel tank leaks
- EVAP system hose leaking
- Fuel tank leaking (not common)

P0442 - Evaporative Emissions System Leak Detected (Small Leak)

P0455 - Evaporative Emissions System Leak Detected (Gross Leak)

This diagnosis detects leaks in the EVAP purge line using engine intake manifold vacuum. If pressure does not increase, the 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.

Causes:
- Missing Fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- Incorrect fuel tank vacuum relief valve
- Leak is in line between intake manifold

Solutions:
- Re-tighten or replace fuel tank filler cap
- Replace damaged or leaking EVAP canister
- Replace damaged or leaking lines.

P0455....Evaporative Emission Control System Leak Detected (gross leak
the first thin to check is your gas cap

CODE PO455 EVAPORATIVE EMISSION SYSTEM LARGE LEAK DETECTED.POSSIBLE CAUSES CANISTER VENT SOLENOID MAY BE STUCK IN OPEN POSITION / EVAP CANISTER TUBE EVAP CANISTER PURGE OUTLET TUBE OR EVAP RETURN TUBE DISCONNECTED OR CRACKED OR CANISTER IS DAMAGED / EVAP CANISTER PURGE VALVE STUCK CLOSED OR CANISTER DAMAGED / FUEL FILLER CAP MISSING LOOSE NOT TIGHT OR THE WRONG PART / FUEL VAPOR HOSES TUBES BLOCKED OR RESTRICED OR FUEL VAPOR CONTROL VALVE TUBE OR FUEL VAPOR VENT VALVE ASSEMBLY BLOCKED /FUEL TANK PRESSURE SENSOR HAS FAILED MECHANICAL FAULT /FUEL TANK CONTROL VALVE IS CONTAMINATED DAMAGED OR HAS FAILED.

Large leak?... Fuel Cap not tight or the wrong one is installed. Also, the charcoal canister close valve may be stuck 'open' AND/OR the purge control solenoid valve may be stuck 'closed.'

First thing to check is the gas cap, make certain it is tight and the cap seal is not damaged or cut. In many cases this is the root cause for the P0455.
If that checks good, you want to check the vacuum hoses from the EVAP purge solenoid under the hood, all the way back to the EVAP canister. Make certain all are connected and not damaged or cracked.
Let me know.
Regards,