Check engine light comes on

SOURCE: what are troubleshooting codes P1684 and P0456?

If both codes came at the same time and you didn't take the battery cable off, you need a purge solenoid, $40 near master cylinder. Put 3/4 tank of gas and the light will go out buy the time you get to 1/4 tank.

SOURCE: I'm looking for the OBD codes for a 2001 Chrystler

http://www.obd-codes.com/

SOURCE: What is the trouble code p1684, and p0455.

1684 is 'battery disconnected in last 50 starts' and should shut off after you have used it for 50 more.
0455 is 'Evaporative emission control system leak detected (gross leak)

SOURCE: CODES,P0442,P0455,P0456,P1684

P0442, P0455 AND P0456 are all evaporative leak monitor test failures (small, medium and large leaks). These codes appear anytime the integrity of the air space above the fuel or the lines to/from the vapor canister or purge valve. If there is no damage to the canister, check the lines that run under the van from the fuel tank and canister to the purge valve (under the hood). Also, check to make sure that the hoses are not split or disconnected where they connect to the purge valve. The P1684 is abit more confusing. This is not a valid DTC for your vehicle. It's possible the scanner the shop you went to is an OTC scanner that is reporting a false code. It's also possible they wrote it down incorrectly. The closest thing that makes any sense is a P1486 which would indicate a pinched hose in the same monitor system as the other 3 codes. Best of luck!