Engine code 456 - 2002 Chrysler Town & Country

456 is a small evap leak check hoses to evap canister by fuel tank.

Code 456 is a common code for a small leak in the evap system. The evap system is how the computer vents gas fumes from the gas tank.
The problem could be a faulty gas cap, the cap left off with the engine running, or something else.

Code P0456 on an Audi is an Evaporative System Emission Leak. You can find more detail here

The generic description for code 456 is a small or large leak in the EVAP system. The computer vents the gas tank to the vapor canister when the engine is running. It also checks the system for leaks.
The gas tank would need to be pressure tested for leaks, including the gas cap.

Evaporative emission control system malfunction
Usually this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could conceivable cause this code as well or if the cap wasn't properly tightened. Any of the following could also be the cause:

• A small leak in any of the EVAP hoses or fuel tank hoses
• A small leak in the purge valve or vent valve
• The EVAP Canister may be leaking

P0456 is Evap Emission control small leak detected.
P0522 Engine oil pressure sensor low voltage.
The first code could be related to a loose, defective, or missing gas cap.
The second code, could be a defective sensor but you will need to confirm. Check oil level and condition first then onto the sensor and related wiring.

the gas cap is the most common if u can reset code do so and if code comes back then need to check-- the fuel lines -purge valve and vent -also the canister--- for cracked disconnected damaged lines

404 is an EGR code
and 456 is gas leak

So probably tighten gas cap or replace gas cap for code 456 then for code 404 clean carbon deposits from EGR valve or replace it then e mail me for a certain test that has to be done at [email protected] thanks

I would start with a test drive with a fuel pressure gauge on it make sure you have spec. 35 - 40 psi. Clear codes and record all the freeze frame data in obd2 as you will need this in the diag process. 442 and 456 are evap codes I believe, do they return with the 300 misfire codes? Either way you need to reproduce the problem with the gauge on it and get the first code it sets. Could be fuel pump/filter/sending unit assy. In this case you will need to pay attention to the fuel level when this occurs. (same level as before)

Could be the gas cap.  Do you fill the tank with the engine running?
Otherwise, check the hoses near the Evap canister.  I have 2003 T&C and had the small leak and large leak codes.  I looked at the evap cansiter and the hose coming from the fuel tank vapor line had a huge crack in it, to the point it had fallen off the evap caniser.  I trimmed the end of the hose and reconnected and voila, no codes.
The evap canister is on the driver's side of the van, underneath, slightly behind the drivers seat.
BTW, to clear the codes without an OBDII reader, remove the negative cable for 5-10 minutes (15 to be safe).  The computer resets and clears the codes, except for one that it sets saying loss of power to the memory.